Rule re-write.

[Nathan S]

For those with short attention spans, the 4th post in this thread (Reply #3) is the one you are looking for. This post, Post #2 and Post #5 are explainations of how and why.
Here's what I've come up with - I'm happy to have a civil discussion, happy to receive constructive input, happy to fix any mistakes (typos and otherwise),happy to change things.
Not so happy to listen to whinging...
At this stage, this is purely an exercise on OzVMX - but hopefully they will be a clear improvement and supported by the majority of punters, and can be published in the MA Manual.

Main goal of the re-write is to make the rules simpler and less ambigous. The problem areas in the current rules have been discussed ad nauseum, so I don't intend on going over it all again...
There is no intention to change the intent of the rules - everyone who has a legal bike under the current rules, should have a legal bike under the re-write.

Please read them all, and take some time to think before posting. Please also have a close look at the current rules before complaining about an omission from the re-write. A lot of long standing rules have been removed or changed in recent years. The handlebar cross-bar pad thing surprised the hell out of me, for example...

OK, so there's the disclaimer over and done with - now let's look at what the current rules are (Sunday 9/2/14, 2pm):
MOMS: http://moms.org.au/
16a, CMX Nationals (Classic & Post Classic): http://moms.org.au/rules/18-classic-motocross-dirt-track/18-1-protective-clothing-classic-motocross-and-dirt-track/
16b, CMX Nationals classes: http://moms.org.au/rules/18-classic-motocross-dirt-track/18-2-eligibility/
16c, CMX Competition rules: http://moms.org.au/rules/18-classic-motocross-dirt-track/18-3-fuel-classic-mx-dirt-track/
16d, CMX Technical Regulations: http://moms.org.au/rules/18-classic-motocross-dirt-track/18-4-machine-and-class-identification-classic-mx-dirt-track/

16a defines Classic & Post-Classic, and the classes that are to be run at National Title meetings.
16b appears to be almost entirely redundant, and should simply disappear. Add clause 16.5 to the end of 16a, and delete the rest of 16b. I also believe that the age class races should be changed to "all eras up to and including Pre-78" for the Classic Nats, and "all eras up to and including pre-90" for the Post Classic Nats. But I am not trying to to change the rules, just clarify them.
16c is about standard requirements and procedures, like the need for scrutiny, numberplate colours, rider clothing, etc. MA-guff, in other words.
16d is about bike eligibility.

Most of the angst comes from 16d, so it deserves to be reproduced in full (NB: This is the current version, not the re-write!):

16.11 MACHINE ELIGIBILITY
16.11.1 Eligible Machines
16.11.1.1    Only machines conforming to the requirements set out in this chapter will be accepted for competition.
16.11.1.2    The onus of proof of eligibility shall rest wholly upon the rider or entrant of the machine. Service and parts manual publication dates are not proof of eligibility.
16.12 SOUND EMISSIONS
16.12.0.1    Sound testing must be carried out at all permitted events; however, it is not mandatory to test all machines.
16.12.1 Specifications
16.12.1.1    Sound emissions are set out in the table below:
30 metres (from side of track) ride by test
DISCIPLINE    

LIMIT dB(A)
Dirt Track & Track (incl. Quads)    95
Record Attempts    

No limit
16.12.2 Sound Control During Competition
16.12.2.1    The Sound Control Officer (SCO) must arrive in sufficient time for discussions with the Clerk of the Course and other Technical Officials in order that a suitable test site and testing policy can be agreed.
16.12.2.2    Machines can be tested before, or after competing in an event, chosen by ballot, or as required by a Steward, Clerk of Course or SCO.
16.12.2.3    Where government regulations or planning orders exist in relation to lower sound emissions or where a venue has lower sound emission requirements as part of the hire contract, the sound emission required will prevail over General Competition Rule 16.12.1.1.
16.12.3 Use of Sound Level Meters
16.12.3.1    Sound testing apparatus must:

    Comply with international standard IEC 651, Type 1 or Type 2.
    Include a compatible calibrator, which must be used immediately before testing begins and always just prior to a re-test if a disciplinary sanction may be imposed.

16.12.3.2    Sound testing apparatus must be set to:

    ‘Fast response’
    ‘A’ weighted,
    Select range High 80~130 dB,
    Activate the function MAX MIN – set on MAX,

16.12.3.3    ‘30 Metre ride by’ test

    The sound levels will be measured with the sound meter/microphone fixed on a tripod, in the horizontal position, 30 metres from the edge of the track at a high speed point.

16.12.3.4    Tests shall not take place in the rain
16.12.4 Machine testing
16.12.4.1    If a machine fails, it can be represented for re-testing.
16.12.4.2    No person may compete in any event on a machine whose noise emissions exceed the prescribed levels.
16.12.4.3    A machine which does not comply with the sound limits can be presented several times.
16.13 FUEL
16.13.1 Fuel Warning
16.13.1.1    Fuels and lubricants are highly specialised substances and participants must be aware they may contain substances that are extremely dangerous to human health if misused, inhaled or allowed to contact skin.
16.13.1.2    Some of the components of fuel and lubricants are suspected of having the potential to cause cancer in rare circumstances.
16.13.1.3    The use of petrol as a general cleaning and washing agent is a common misuse of a potentially dangerous substance.
16.13.1.4    Fuels should be used and stored with extreme care and in accordance with the manufacturer’s instructions.
16.13.2 Fuel Testing
16.13.2.1    For any event, meeting or series, the relevant controlling body may direct that no fuels other than fuels of prescribed specifications and from a prescribed source may be used.

    Tests to ensure that only prescribed fuels are used in an event, meeting or series may be administered at any time and place during the course of the same,
    The Clerk of Course, Race Director or Chief Scrutineer may direct the administration of fuel tests.

16.13.2.2    Fuel tests must comply with the following procedures:

    All containers for holding samples must be clean and constructed of robust non-reactive impermeable material, must be sealable, and must have provision for identification,
    Equipment used for the extraction of fuel from machines must be clean and constructed of fuel non-reactive material,
    All samples must be divided into two lots (Sample A and Sample B) of not less than 5ml each, which must be placed in separate containers,
    Once samples are placed in containers, the containers must immediately be sealed and identified by reference to the machine from which the sample was taken. This information must be entered on a fuel sample certificate which must certify the date, place and time of taking the sample, the identity of the machine from which the sample was taken and the identity of the rider,
    Both samples must remain in the control of the official who administered the test.
    The rider or the representative must sign the fuel sample certificate acknowledging samples have been taken and are sealed,
    All samples held by the official must be delivered as soon as practicable after the competition to the relevant controlling body which must deliver the Sample A as soon as practicable to a laboratory approved by MA where they must be tested for content and quality in accordance with standard scientific procedures,
    The relevant controlling body must as soon as practicable after receipt of the results notify the rider or rider’s team representative and MA,
    If the rider is dissatisfied with the test result of sample A, they may request sample B be tested at an MA approved laboratory in their presence.

16.13.3 Refuelling
16.13.3.1    During refuelling, each machine must be stationary with the engine stopped.
16.13.3.2    Refuelling will be deemed to have commenced when the fuel tank has been opened and completed when the tank is closed.
16.13.3.3    Smoking is strictly prohibited in areas where refuelling is permitted.
16.13.3.4    Riders are liable for exclusion from an event for failing to adhere to General Competition Rule 16.13.3.3, and are responsible for the actions of their mechanics and support team members.
16.13.4 Homologation of Fuel
16.13.4.1    Unleaded fuel produced by an oil company for sale in the Australian general transport fuel market through retail petrol pumps in at least five states does not have to be homologated. For the avoidance of doubt this means the fuel must be available for sale on demand from a roadside bowser outlet at each of at least five separate service stations in each of at least five Australian states or territories.
16.13.4.2    Organisations seeking homologation of fuel must provide MA with:

    Two one-litre sealed containers of the fuel for analysis,
    Details of the fuels characteristics,
    The distribution network,
    The price structure,
    A homologation fee of $2,500 in the first year and $2,000 per year thereafter.

16.13.4.3    Fuels approved under this General Competition Rule will be published at www.ma.org.au.
16.13.5 Fuel: Classic Motocross and Classic Dirt Track
   Classic Motocross and Classic Dirt Track fuel used for competition must be:

    ure methanol with no additives other than lubricating oil, or,
    Unleaded fuel that is no more than 100 RON and meets rule 16.13.4.1,
    Which contains no additives other than those added at the point of manufacture except for lubricating oil, or,
    Be a brand of fuel homologated by MA that is compatible with the “Fuel Quality Standards Act 2000”, or,
    Leaded fuel provided that the fuel is purchased from suppliers approved by Environmental Australia.

16.14 ENGINES: GENERAL
16.14.1 Reciprocating Engines
16.14.1.1    Cubic capacity = (D2 x 3.1416 x C x N)
4Where:
D = Bore in centimetres,
C = stroke in centimetres,
N = Number of cylinders.
16.14.2 Engine capacity tolerances
16.14.2.1    The actual engine capacity of a machine competing in a capacity class may not exceed the prescribed capacity for that class by more than 5%.
16.15 MACHINES AND COMPONENTS
16.15.1 Centre and Side Stands
16.15.1.1    Centre and side stands must be removed for all types of competition
16.15.2 Handlebars
16.15.2.1    The ends of the handlebars or twist grip sleeves must be securely plugged so as to present a flush or rounded end.
16.15.2.2    Handlebar levers must:

    Have ball ends with a minimum diameter of:
        15mm, for levers longer than 76mm,
        10mm, for levers shorter than 76mm.
    Measure no more than 200mm from the fulcrum to the extremity of the ball.

16.15.2.3    Throttle controls must be self-closing.
16.15.3 Kick Start Levers
16.15.3.1    Kick start levers, other than transverse, must be folding.
16.15.4 Drive Chain Protection
16.15.4.1    Primary drives (the drive connecting engine to clutch) must be guarded so as to prevent direct access to the chain or sprockets with the fingers.
16.15.4.2    The guard must be constructed of:

    Metal having a minimum thickness of 1.6mm, which may be mesh or expanded metal provided the openings do not exceed 10mm, or
    Fibreglass having a minimum thickness of 3mm.

16.15.4.3    If a plastic, fibreglass or part open chain guard is used, a steel bolt of not less than 10mm diameter, placed outside the bottom rear quadrant of the clutch sprocket. This bolt, if damaged, must be replaced.
16.15.4.4    Projecting sprockets, which are not behind a clutch assembly or directly behind a frame member, must be guarded where the sprocket teeth are further than 30mm from a frame member or swinging arm.
16.15.4.5    A counter shaft sprocket which is more than 30mm from the outside of the swing arm pivot must be covered.
 16.15.4.6    Other than CMX/CDT A chain guard made of suitable material must be fitted in a way to prevent trapping between the lower drive chain run and the final drive sprocket at the rear wheel.
16.15.5 Tyres
16.15.5.1    Tyres must comply with the following:

    Metal studs, spikes, chain, rope or other non-skid attachments may not be used unless permitted by the relevant Supplementary Regulations.
    Paddle or scoop treaded tyres may not be fitted.

16.15.5.2    Valve caps must be used for all competitions.
16.15.6 Mudguards
16.15.6.1    Either a rear mudguard or a seat must be fitted which extends at least 20 degrees to the rear of a vertical line drawn through the rear wheel axle.
16.15.6.2    Mudguards must be made of a material, which is not liable to cause personal injury if deformed.
16.15.7 Acceptable machines and components: Pre 60 Solo
16.15.7.1    Acceptable for the pre 60 class are machines and components built up to and including the 1959 model. The only exception to this General Competition Rule is where the model remains unaltered after this date.
16.15.7.2    Frames of any manufacture are acceptable within the suspension criteria and considerate of the era.
16.15.7.3    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle. Rear shock absorbers will be in the original position using the original mounting points.
16.15.7.4    Plastic and fibreglass is not permitted.
16.15.7.5    Engines and gearboxes must remain externally unchanged.
16.15.7.6    Period carburettors or Amal Mk1 Concentric.
16.15.7.7    Exhaust may be modified but must follow the original lines and meet sound control regulations in GCR 16.12.
16.15.7.8    Folding footrests must be fitted.
16.15.7.9    Countershaft sprocket covers will be fitted.
16.15.8 Acceptable machines and components: Pre 65 Solo
16.15.8.1    Acceptable for the pre 65 class are machines and components built up to and including the 1964 model. The only exception to this rule is where the model remains unaltered after this date.
16.15.8.2    Frames of any manufacture are acceptable within the suspension criteria and considerate of the era.
16.15.8.3    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle.
16.15.8.4    Rear shock absorbers will be in the original position using the original mounting points.
16.15.8.5    Engines and gearboxes must remain externally unchanged.
16.15.8.6    Carburettors of any type pre 75 round slide may be used.
16.15.8.7    Exhaust may be modified but must follow the original lines and meet sound control regulations in GCR 16.12.
16.15.8.8    Folding footrests must be fitted.
16.15.8.9    Countershaft sprocket covers will be fitted.
16.15.9 Acceptable machines and components: Pre 70 Solo
16.15.9.1    Acceptable for the pre 70 class are machines and components built up to and including the 1969 model. The only exception to this rule is where the model remains unaltered after this date.
16.15.9.2    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle. Rear shock absorbers will be in the original position using the original mounting points.
16.15.9.3    Engines and gearboxes must remain externally unchanged.
16.15.9.4    Carburettors; any type of pre 75 round slide may be used.
16.15.9.5    No reed valves permitted.
16.15.9.6    Exhaust may be modified but must follow the original lines and meet sound control regulations in GCR 16.12.
16.15.9.7    Folding footrests must be fitted.
16.15.9.8    Countershaft sprocket covers will be fitted.
16.15.9.9    Yamaha XS1 and XS650 engines are eligible.
16.15.9.10    Acceptable follow on models pre 70

    AJS Stormer 250,
    Greeves griffon models,
    Yamaha AT1, DT1, CT1, RT1 pre reed block.

16.15.10 Acceptable machines and components: Pre 75 Solo
16.15.10.1    Acceptable for the pre 75 class are machines and components built up to and including the 1974 model. The only exception to this rule is where the model remains unaltered after this date.
16.15.10.2    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle. Rear shock absorbers will be in the original position using the original mounting points.
16.15.10.3    Engines and gearboxes must remain externally unchanged.
16.15.10.4    Carburettors; any type of pre 75 round slide may be used.
16.15.10.5    XS1 and XS650 engines are eligible.
16.15.10.6    Exhaust may be modified but must follow the original lines and meet sound control regulations in GCR 16.12.
16.15.10.7    Folding footrests must be fitted.
16.15.10.8    Countershaft sprocket covers will be fitted.
16.15.10.9    Acceptable follow on models pre 75

    Honda CR125M1, XL250K1, XL350K1, MT250 and MT125
    Yamaha YZ360B, DT250B,
    Suzuki TS400 (all).

16.15.11 Acceptable machines and components: Pre 78 Solo
16.15.11.1    Acceptable for the pre 78 classes:
a) Machines and components that are limited to the 1975, 1976, 1977 models alone. The only exception to this rule is where the model remains unaltered after this date.
b) Pre 78 Women’s class: acceptable machines and components are up to and including the 1977 model year. The only exception to this rule is where the model remains unaltered after this date.
16.15.11.2    Front wheel travel will not exceed 229mm (9 inches) rear wheel travel will be limited to 229mm (9 inches) measured at the axle. Rear shock absorbers will be in the original position using the original mounting points.
16.15.11.3    Engines and gearboxes must remain externally unchanged.
16.15.11.4    Carburettors; any type of pre 78 round slide may be used.
16.15.11.5    Exhaust may be modified but must follow the original lines and meet sound control regulations in GCR 16.12.
16.15.11.6    Folding footrests must be fitted.
16.15.11.7    Countershaft sprocket covers will be fitted.
16.15.11.8    Acceptable follow on models pre 78

    CZ 125 1978, CZ400 1978,
    Montesa VB (must comply to suspension limits),
    Yamaha TT500 1978.

16.15.12 Acceptable machines and components: Evolution Class Solo
16.15.12.1    Bikes will be OEM (original equipment manufacturer).
16.15.12.2    Modifications converting later equipment to comply will not be allowed.
16.15.12.3    All components will be of the period the machine was manufactured:

    No linkage suspension,
    No disk brakes,
    Air cooled motors.

16.15.12.4    Carburettors; period flat slide carburettors and any round slide carburettor may be used.
16.15.12.5    Engines and gearboxes must remain externally unchanged.
16.15.12.6    Exhaust may be modified but must follow the original lines and be fitted with an effective muffler.
16.15.12.7    Folding footrests must be fitted.
16.15.12.8    Countershaft sprocket covers will be fitted.
16.15.12.9    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.
16.15.13 Acceptable machines and components: Pre 85 Solo
16.15.13.1    Acceptable for the pre 85 class are machines and components built up to and including the 1984 model. The only exception to this rule is where the model remains unaltered after this date.
16.15.13.2    Carburettors; period flat slide carburettors and any round slide carburettor may be used.
16.15.13.3    Engines and gearboxes must remain externally unchanged.
16.15.13.4    Exhaust may be modified but must follow the original lines and be fitted with an effective muffler.
16.15.13.5    Folding footrests must be fitted.
16.15.13.6    Countershaft sprocket covers will be fitted.
16.15.13.7    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.
16.15.14 Acceptable machines and components: Pre 90 Solo
16.15.14.1    Acceptable for the pre 90 class are machines and components built up to and including the 1989 model. The only exception to this rule is where the model remains unaltered after this date.
16.15.14.2    Carburettors; period flat slide carburettors and any round slide carburettor may be used.
16.15.14.3    Engines and gearboxes must remain externally unchanged.
16.15.14.4    Exhaust may be modified but must follow the original lines and be fitted with an effective muffler.
16.15.14.5    Folding footrests must be fitted.
16.15.14.6    Countershaft sprocket covers will be fitted.
16.15.14.7    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.
16.16 SLIDERS
16.16.1 Slider Frames
16.16.1.1    The frame must:

    Have a conventional swing arm rear suspension with twin shock absorbers,
    Have a front wheel diameter of 23”,
    Have a rear wheel diameter of 19”,
    Have rear tyres with a maximum tread pattern depth of 8mm,
    Not be fitted with leading-link front forks.

16.16.2 Slider Solo Engines
16.16.2.1    The slider engine must:

    Be a single cylinder,
    When four stroke be 2- valve push rod operation,
    Have a single spark plug,
    Be vertical in the chassis,
    Be fitted with a round slide carburettor, or
    Be a period two stroke compatible with class entered.

16.16.3 Slider Gearbox: Classic Long Track
16.16.3.1    The gearbox must have at least two gears.
16.16.4 Slider Sidecar Frames
16.16.4.1    Conventional type frames as used prior to 31st December 1976 must be used.
16.16.5 Slider Sidecar Engines
16.16.5.1    Engines must have been manufactured before 31st December 1976.
16.17 SIDECARS
16.17.1 All Classes
16.17.1.1    Left -hand and right -hand sidecars may compete against each other in Classic Motocross.
16.17.2 Frames and Parts
16.17.2.1    For the Pre-1975 classes, all performance parts except frames must be manufactured before 31st December 1974 and must comply with the following:

        Wheel track measurement, taken between the longitudinal centres of the rear and sidecar wheels must be between 810mm and 1100mm,
        The minimum ground clearance must be 175mm unladen,
        The maximum lean of the motorcycle at saddle height mustbe 50mm,
        The dimensions of the sidecar baseboard in plain view, taken from a line drawn no further rearwards than the lowest point of the front down-tube to the forward most point of the sidecar wheel tyre and terminating no further rearwards than a line drawn at right angles to the machine from the rearmost point of the rear tyre, must be:
            At least 760mm long adjacent to the sidecar wheel,
            At least 300mm wide with at least 25mm radius to all corners.
        There must be no more than 50mm between baseboard and motorcycle and between baseboard and sidecar wheel. The baseboard must be arranged so as not to allow the passenger’s feet to be trapped,
        There must be no less than 4 sidecar attachment points,
        Stirrup fitting for the passenger’s feet are not permitted,
        Handholds:
            Must be finished with a loop of at least 100mm,
            Must not project beyond a line taken with the outer edge of the sidecar mudguard or bodywork,
            Adjacent to the nose section of the sidecar and less than 200mm from the track surface must be at an angle of at least 45° from the horizontal.
        The rear end of the rear wheel mudguard must terminate not more than 65° above a horizontal line drawn through the rear wheel axle and be valanced to baseboard level on the inside,
        The sidecar mudguard must cover at least 135° of the periphery of the wheel and be valanced to baseboard level on the inside,
        No machine may be fitted with scoop or paddle tyres,
        Suspension travel must not exceed:
            152mm (6”) 178mm (7”) measured at the front axle,
            102mm (4”) at the rear axle.
        Rear tyre width must not exceed 135mm (5.3”),
        Brakes:
            Front – single caliper, single disc may be fitted provided they were manufactured before 31st December 1974,
            Rear – rear disc brakes may be used provided they were fitted as standard equipment for that particular combination.

    Only round-slide carburettors manufactured within the relevant period may be used,
    Engine capacity must be up to 1300cc.

16.17.2.2    Pre-1985 is for sidecars constructed with motors manufactured before 31st December 1984.
16.17.2.3    A lanyard operated ignition cut-out switch, operating on the primary circuit, must be fitted to the following with a maximum length of one metre:
DISCIPLINE
   
MACHINE
Motocross    Sidecars
Dirt track    Sidecars
16.17.2.4    Pre-1968 will be for sidecars constructed from road going frames and all major components are those commercially available within the period.
16.17.2.5    The following table sets out the machines and components which eligibility scrutineers may use as a guide in determining eligibility. Entrants must prove eligibility of machines not listed below.
MAKE
   
MODEL(S)
Wasp    All up to and including RT2, RT8 and RT14
Hagon    All up to 31st December 1974
Yamaha    XS 650 all models
Honda    Any K series
Norton    All 750, 850 to Mk2 only
Westlake    All up to 850cc and 31st December 1974
Triumph    All up to T150
CCM    All BSA B50 based models

[Ted]

Is it any wonder Vinduros have become so popular

[Nathan S]

Indeed, Ted...


--------------------


So... here's the first part of what I propose:

16.12, 16.13, 16.14, 16.15 up to and including 16.15.5 are all moved to section 16c. They are important (to MA...) but having them in with the specific CMX machine requirements just confuses the issue.

16.15.4.6 is simply deleted - there's no point in having a rule that instantly disqualifies itself.

So far, there's been a change to formatting and removed one rule that does nothing (16.15.4.6) - no other changes.
The rules we now have look like this:

---------------------------------

16.11 MACHINE ELIGIBILITY
16.11.1 Eligible Machines
16.11.1.1    Only machines conforming to the requirements set out in this chapter will be accepted for competition.
16.11.1.2    The onus of proof of eligibility shall rest wholly upon the rider or entrant of the machine. Service and parts manual publication dates are not proof of eligibility.



16.15.7 Acceptable machines and components: Pre 60 Solo
16.15.7.1    Acceptable for the pre 60 class are machines and components built up to and including the 1959 model. The only exception to this General Competition Rule is where the model remains unaltered after this date.
16.15.7.2    Frames of any manufacture are acceptable within the suspension criteria and considerate of the era.
16.15.7.3    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle. Rear shock absorbers will be in the original position using the original mounting points.
16.15.7.4    Plastic and fibreglass is not permitted.
16.15.7.5    Engines and gearboxes must remain externally unchanged.
16.15.7.6    Period carburettors or Amal Mk1 Concentric.
16.15.7.7    Exhaust may be modified but must follow the original lines and meet sound control regulations in GCR 16.12.
16.15.7.8    Folding footrests must be fitted.
16.15.7.9    Countershaft sprocket covers will be fitted.
16.15.8 Acceptable machines and components: Pre 65 Solo
16.15.8.1    Acceptable for the pre 65 class are machines and components built up to and including the 1964 model. The only exception to this rule is where the model remains unaltered after this date.
16.15.8.2    Frames of any manufacture are acceptable within the suspension criteria and considerate of the era.
16.15.8.3    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle.
16.15.8.4    Rear shock absorbers will be in the original position using the original mounting points.
16.15.8.5    Engines and gearboxes must remain externally unchanged.
16.15.8.6    Carburettors of any type pre 75 round slide may be used.
16.15.8.7    Exhaust may be modified but must follow the original lines and meet sound control regulations in GCR 16.12.
16.15.8.8    Folding footrests must be fitted.
16.15.8.9    Countershaft sprocket covers will be fitted.
16.15.9 Acceptable machines and components: Pre 70 Solo
16.15.9.1    Acceptable for the pre 70 class are machines and components built up to and including the 1969 model. The only exception to this rule is where the model remains unaltered after this date.
16.15.9.2    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle. Rear shock absorbers will be in the original position using the original mounting points.
16.15.9.3    Engines and gearboxes must remain externally unchanged.
16.15.9.4    Carburettors; any type of pre 75 round slide may be used.
16.15.9.5    No reed valves permitted.
16.15.9.6    Exhaust may be modified but must follow the original lines and meet sound control regulations in GCR 16.12.
16.15.9.7    Folding footrests must be fitted.
16.15.9.8    Countershaft sprocket covers will be fitted.
16.15.9.9    Yamaha XS1 and XS650 engines are eligible.
16.15.9.10    Acceptable follow on models pre 70

    AJS Stormer 250,
    Greeves griffon models,
    Yamaha AT1, DT1, CT1, RT1 pre reed block.

16.15.10 Acceptable machines and components: Pre 75 Solo
16.15.10.1    Acceptable for the pre 75 class are machines and components built up to and including the 1974 model. The only exception to this rule is where the model remains unaltered after this date.
16.15.10.2    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle. Rear shock absorbers will be in the original position using the original mounting points.
16.15.10.3    Engines and gearboxes must remain externally unchanged.
16.15.10.4    Carburettors; any type of pre 75 round slide may be used.
16.15.10.5    XS1 and XS650 engines are eligible.
16.15.10.6    Exhaust may be modified but must follow the original lines and meet sound control regulations in GCR 16.12.
16.15.10.7    Folding footrests must be fitted.
16.15.10.8    Countershaft sprocket covers will be fitted.
16.15.10.9    Acceptable follow on models pre 75

    Honda CR125M1, XL250K1, XL350K1, MT250 and MT125
    Yamaha YZ360B, DT250B,
    Suzuki TS400 (all).

16.15.11 Acceptable machines and components: Pre 78 Solo
16.15.11.1    Acceptable for the pre 78 classes:
a) Machines and components that are limited to the 1975, 1976, 1977 models alone. The only exception to this rule is where the model remains unaltered after this date.
b) Pre 78 Women’s class: acceptable machines and components are up to and including the 1977 model year. The only exception to this rule is where the model remains unaltered after this date.
16.15.11.2    Front wheel travel will not exceed 229mm (9 inches) rear wheel travel will be limited to 229mm (9 inches) measured at the axle. Rear shock absorbers will be in the original position using the original mounting points.
16.15.11.3    Engines and gearboxes must remain externally unchanged.
16.15.11.4    Carburettors; any type of pre 78 round slide may be used.
16.15.11.5    Exhaust may be modified but must follow the original lines and meet sound control regulations in GCR 16.12.
16.15.11.6    Folding footrests must be fitted.
16.15.11.7    Countershaft sprocket covers will be fitted.
16.15.11.8    Acceptable follow on models pre 78

    CZ 125 1978, CZ400 1978,
    Montesa VB (must comply to suspension limits),
    Yamaha TT500 1978.

16.15.12 Acceptable machines and components: Evolution Class Solo
16.15.12.1    Bikes will be OEM (original equipment manufacturer).
16.15.12.2    Modifications converting later equipment to comply will not be allowed.
16.15.12.3    All components will be of the period the machine was manufactured:

    No linkage suspension,
    No disk brakes,
    Air cooled motors.

16.15.12.4    Carburettors; period flat slide carburettors and any round slide carburettor may be used.
16.15.12.5    Engines and gearboxes must remain externally unchanged.
16.15.12.6    Exhaust may be modified but must follow the original lines and be fitted with an effective muffler.
16.15.12.7    Folding footrests must be fitted.
16.15.12.8    Countershaft sprocket covers will be fitted.
16.15.12.9    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.
16.15.13 Acceptable machines and components: Pre 85 Solo
16.15.13.1    Acceptable for the pre 85 class are machines and components built up to and including the 1984 model. The only exception to this rule is where the model remains unaltered after this date.
16.15.13.2    Carburettors; period flat slide carburettors and any round slide carburettor may be used.
16.15.13.3    Engines and gearboxes must remain externally unchanged.
16.15.13.4    Exhaust may be modified but must follow the original lines and be fitted with an effective muffler.
16.15.13.5    Folding footrests must be fitted.
16.15.13.6    Countershaft sprocket covers will be fitted.
16.15.13.7    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.
16.15.14 Acceptable machines and components: Pre 90 Solo
16.15.14.1    Acceptable for the pre 90 class are machines and components built up to and including the 1989 model. The only exception to this rule is where the model remains unaltered after this date.
16.15.14.2    Carburettors; period flat slide carburettors and any round slide carburettor may be used.
16.15.14.3    Engines and gearboxes must remain externally unchanged.
16.15.14.4    Exhaust may be modified but must follow the original lines and be fitted with an effective muffler.
16.15.14.5    Folding footrests must be fitted.
16.15.14.6    Countershaft sprocket covers will be fitted.
16.15.14.7    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.
16.16 SLIDERS
16.16.1 Slider Frames
16.16.1.1    The frame must:

    Have a conventional swing arm rear suspension with twin shock absorbers,
    Have a front wheel diameter of 23”,
    Have a rear wheel diameter of 19”,
    Have rear tyres with a maximum tread pattern depth of 8mm,
    Not be fitted with leading-link front forks.

16.16.2 Slider Solo Engines
16.16.2.1    The slider engine must:

    Be a single cylinder,
    When four stroke be 2- valve push rod operation,
    Have a single spark plug,
    Be vertical in the chassis,
    Be fitted with a round slide carburettor, or
    Be a period two stroke compatible with class entered.

16.16.3 Slider Gearbox: Classic Long Track
16.16.3.1    The gearbox must have at least two gears.
16.16.4 Slider Sidecar Frames
16.16.4.1    Conventional type frames as used prior to 31st December 1976 must be used.
16.16.5 Slider Sidecar Engines
16.16.5.1    Engines must have been manufactured before 31st December 1976.
16.17 SIDECARS
16.17.1 All Classes
16.17.1.1    Left -hand and right -hand sidecars may compete against each other in Classic Motocross.
16.17.2 Frames and Parts
16.17.2.1    For the Pre-1975 classes, all performance parts except frames must be manufactured before 31st December 1974 and must comply with the following:

        Wheel track measurement, taken between the longitudinal centres of the rear and sidecar wheels must be between 810mm and 1100mm,
        The minimum ground clearance must be 175mm unladen,
        The maximum lean of the motorcycle at saddle height mustbe 50mm,
        The dimensions of the sidecar baseboard in plain view, taken from a line drawn no further rearwards than the lowest point of the front down-tube to the forward most point of the sidecar wheel tyre and terminating no further rearwards than a line drawn at right angles to the machine from the rearmost point of the rear tyre, must be:
            At least 760mm long adjacent to the sidecar wheel,
            At least 300mm wide with at least 25mm radius to all corners.
        There must be no more than 50mm between baseboard and motorcycle and between baseboard and sidecar wheel. The baseboard must be arranged so as not to allow the passenger’s feet to be trapped,
        There must be no less than 4 sidecar attachment points,
        Stirrup fitting for the passenger’s feet are not permitted,
        Handholds:
            Must be finished with a loop of at least 100mm,
            Must not project beyond a line taken with the outer edge of the sidecar mudguard or bodywork,
            Adjacent to the nose section of the sidecar and less than 200mm from the track surface must be at an angle of at least 45° from the horizontal.
        The rear end of the rear wheel mudguard must terminate not more than 65° above a horizontal line drawn through the rear wheel axle and be valanced to baseboard level on the inside,
        The sidecar mudguard must cover at least 135° of the periphery of the wheel and be valanced to baseboard level on the inside,
        No machine may be fitted with scoop or paddle tyres,
        Suspension travel must not exceed:
            152mm (6”) 178mm (7”) measured at the front axle,
            102mm (4”) at the rear axle.
        Rear tyre width must not exceed 135mm (5.3”),
        Brakes:
            Front – single caliper, single disc may be fitted provided they were manufactured before 31st December 1974,
            Rear – rear disc brakes may be used provided they were fitted as standard equipment for that particular combination.

    Only round-slide carburettors manufactured within the relevant period may be used,
    Engine capacity must be up to 1300cc.

16.17.2.2    Pre-1985 is for sidecars constructed with motors manufactured before 31st December 1984.
16.17.2.3    A lanyard operated ignition cut-out switch, operating on the primary circuit, must be fitted to the following with a maximum length of one metre:
DISCIPLINE
   
MACHINE
Motocross    Sidecars
Dirt track    Sidecars
16.17.2.4    Pre-1968 will be for sidecars constructed from road going frames and all major components are those commercially available within the period.
16.17.2.5    The following table sets out the machines and components which eligibility scrutineers may use as a guide in determining eligibility. Entrants must prove eligibility of machines not listed below.
MAKE
   
MODEL(S)
Wasp    All up to and including RT2, RT8 and RT14
Hagon    All up to 31st December 1974
Yamaha    XS 650 all models
Honda    Any K series
Norton    All 750, 850 to Mk2 only
Westlake    All up to 850cc and 31st December 1974
Triumph    All up to T150
CCM    All BSA B50 based models

[Nathan S]

And then, finally, we get to the re-write!
I've ADDED quite a bit of stuff, but the word count is still substantially less than it was (not including the MA guff that I sent off to 16c) - so I've had a win on that bit, at least...



---------------------------------------------------------

16.11 MACHINE ELIGIBILITY
16.11.1 Eligible Machines
16.11.1.1    Only machines conforming to the requirements set out in chapter 16 will be accepted for competition.
16.11.1.2    The onus of proof of eligibility shall rest wholly upon the rider or entrant of the machine. Service and parts manual publication dates are not proof of eligibility.



16.15.7 Acceptable machines and components:
All Eras:
a) Major Components are: Frame, swing arm, forks, wheel hubs, triple clamps, engine cases, cylinder(s), and cylinder head(s). A machine's era will be defined by its newest major component.
b) Any major component that is visually similar and operationally indistinguishable from the original will be accepted regardless of the date of manufacture.
ba) Any major component that is visually similar and operationally indistinguishable from aftermarket components available in the era, will be accepted regardless of the date of manufacture.
c) Any modifications to major components must be using principles and techniques that were available in the era the machine is entered in.
d) Rear shock absorbers will be in the original position(s), using the original mounting points.
da) Folding footrests must be fitted.

Pre 60 Solo. This class is intended to represent the formative era of motocross.
16.15.7.1     The pre 60 class is for machines that closely represent those built up to (and including) 1959 models.
16.15.7.3    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle.
16.15.7.4    Plastic and fibreglass is not permitted.
16.15.7.6     Period carburettors or Amal Mk1 Concentric.
16.15.7.7         Reed valves are not permitted.

Pre 65 Solo. This class is intended to represent the first generation of purpose-built motocross bikes.
16.15.8.1    The pre 65 class is for machines that closely represent those that were built up to (and including) 1964 models.
16.15.8.3    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle.
16.15.8.6    Carburettors of any type pre 75 round slide may be used.
16.15.8.7         Reed valves are not permitted.

Pre 70. This class is intended to represent the era where 2-stroke machines became dominant.
16.15.9.1     The pre 70 class is for machines that closely represent those built up to (and including) 1969 models.
16.15.9.2     Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle.
16.15.9.4     Carburettors; any type of pre 75 round slide may be used.
16.15.9.5     Reed valves are not permitted.
16.15.9.9    Yamaha XS1 and XS650 engines are eligible.
16.15.9.10    Acceptable follow on models:  AJS Stormer 250;  Greeves griffon models; Yamaha AT1, DT1, CT1, RT1 pre reed block.

Pre 75 Solo. This class is intended to represent the end of the short travel suspension era.
16.15.10.1    The pre 75 class is for machines that closely represent those built up to (and including) 1974 models.
16.15.10.2    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle.
16.15.10.4    Carburettors; any type of pre 75 round slide may be used.
16.15.10.5    XS1 and XS650 engines are eligible.
16.15.10.9    Acceptable follow on models pre 75:
    Honda CR125M1, XL250K1, XL350K1, MT250 (all) and MT125 (all)
    Yamaha YZ360B, DT250B,
    Suzuki TS400 (all).

Pre 78 Solo and Women's Pre-78. This class is intended to represent the transition era between the short travel Pre-75 machines and the long travel Evo machines.
16.15.11.1    The pre 78 class is for machines that closely represent those built up to (and including) 1977 models.
16.15.11.2    Front wheel travel will not exceed 229mm (9 inches) rear wheel travel will be limited to 229mm (9 inches) measured at the axle.
16.15.11.4    Carburettors; any type of pre 78 round slide may be used.
16.15.11.8     Acceptable follow on models pre 78

    CZ 125 1978, CZ400 1978,
    Montesa VB (must comply to suspension limits),
    Yamaha TT500 1978.

Evolution. This class is intended to represent the era of long suspension travel, before water-cooling, disc brakes and linkage rear suspension became dominant.
16.15.12.1    The Evo class is for machines that use drum brakes, air-cooling and non-linkage rear suspension, as was commonplace until 1981. It also allows for later machines up to (and including) 1985 models that retained this technology.
e) Evolution class bikes must have  Non-linkage rear suspension, No disc brakes, and Air cooled motors.
16.15.12.4    Carburettors; period flat slide carburettors and any round slide carburettor may be used.
16.15.12.9    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.

Pre 85 Solo. This class is intended to represent the era of the first generation of disc front brakes, water cooling, linkage rear suspension and exhaust power valves.
16.15.13.1    The pre 85 class is for machines that closely represent those built up to (and including) 1984 models.
16.15.13.2     Carburettors; pre-85 flat slide carburettors and any round slide carburettor may be used.
16.15.13.7    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.

Pre 90 Solo. This class is intended to represent the era where rear disc brakes, upside down forks, and the second generation of exhaust power valves became common place.
16.15.14.1    The pre 90 class is for machines that closely represent those built up to (and including) 1989 models.
16.15.14.2    Carburettors; period flat slide carburettors and any round slide carburettor may be used.
16.15.14.7    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.

16.16 SLIDERS
16.16.1 Slider Frames
16.16.1.1    The frame must:

    Have a conventional swing arm rear suspension with twin shock absorbers,
    Have a front wheel diameter of 23”,
    Have a rear wheel diameter of 19”,
    Have rear tyres with a maximum tread pattern depth of 8mm,
    Not be fitted with leading-link front forks.

16.16.2 Slider Solo Engines
16.16.2.1    The slider engine must:

    Be a single cylinder,
    When four stroke be 2- valve push rod operation,
    Have a single spark plug,
    Be vertical in the chassis,
    Be fitted with a round slide carburettor, or
    Be a period two stroke compatible with class entered.

16.16.3 Slider Gearbox: Classic Long Track
16.16.3.1    The gearbox must have at least two gears.
16.16.4 Slider Sidecar Frames
16.16.4.1    Conventional type frames as used prior to 31st December 1976 must be used.
16.16.5 Slider Sidecar Engines
16.16.5.1    Engines must have been manufactured before 31st December 1976.
16.17 SIDECARS
16.17.1 All Classes
16.17.1.1    Left -hand and right -hand sidecars may compete against each other in Classic Motocross.
16.17.2 Frames and Parts
16.17.2.1    For the Pre-1975 classes, all performance parts except frames must be manufactured before 31st December 1974 and must comply with the following:

        Wheel track measurement, taken between the longitudinal centres of the rear and sidecar wheels must be between 810mm and 1100mm,
        The minimum ground clearance must be 175mm unladen,
        The maximum lean of the motorcycle at saddle height mustbe 50mm,
        The dimensions of the sidecar baseboard in plain view, taken from a line drawn no further rearwards than the lowest point of the front down-tube to the forward most point of the sidecar wheel tyre and terminating no further rearwards than a line drawn at right angles to the machine from the rearmost point of the rear tyre, must be:
            At least 760mm long adjacent to the sidecar wheel,
            At least 300mm wide with at least 25mm radius to all corners.
        There must be no more than 50mm between baseboard and motorcycle and between baseboard and sidecar wheel. The baseboard must be arranged so as not to allow the passenger’s feet to be trapped,
        There must be no less than 4 sidecar attachment points,
        Stirrup fitting for the passenger’s feet are not permitted,
        Handholds:
            Must be finished with a loop of at least 100mm,
            Must not project beyond a line taken with the outer edge of the sidecar mudguard or bodywork,
            Adjacent to the nose section of the sidecar and less than 200mm from the track surface must be at an angle of at least 45° from the horizontal.
        The rear end of the rear wheel mudguard must terminate not more than 65° above a horizontal line drawn through the rear wheel axle and be valanced to baseboard level on the inside,
        The sidecar mudguard must cover at least 135° of the periphery of the wheel and be valanced to baseboard level on the inside,
        No machine may be fitted with scoop or paddle tyres,
        Suspension travel must not exceed:
            152mm (6”) 178mm (7”) measured at the front axle,
            102mm (4”) at the rear axle.
        Rear tyre width must not exceed 135mm (5.3”),
        Brakes:
            Front – single caliper, single disc may be fitted provided they were manufactured before 31st December 1974,
            Rear – rear disc brakes may be used provided they were fitted as standard equipment for that particular combination.

    Only round-slide carburettors manufactured within the relevant period may be used,
    Engine capacity must be up to 1300cc.

16.17.2.2    Pre-1985 is for sidecars constructed with motors manufactured before 31st December 1984.
16.17.2.3    A lanyard operated ignition cut-out switch, operating on the primary circuit, must be fitted to the following with a maximum length of one metre:
DISCIPLINE
   
MACHINE
Motocross    Sidecars
Dirt track    Sidecars
16.17.2.4    Pre-1968 will be for sidecars constructed from road going frames and all major components are those commercially available within the period.
16.17.2.5    The following table sets out the machines and components which eligibility scrutineers may use as a guide in determining eligibility. Entrants must prove eligibility of machines not listed below.
MAKE
   
MODEL(S)
Wasp    All up to and including RT2, RT8 and RT14
Hagon    All up to 31st December 1974
Yamaha    XS 650 all models
Honda    Any K series
Norton    All 750, 850 to Mk2 only
Westlake    All up to 850cc and 31st December 1974
Triumph    All up to T150
CCM    All BSA B50 based models

[Nathan S]

Now that lots of people's brains have exploded, here's the same rules with annotations in blue. (The blue bits aren't part of the rules - they help people understand the changes).

16.11 MACHINE ELIGIBILITY
16.11.1 Eligible Machines
16.11.1.1    Only machines conforming to the requirements set out in chapter 16 will be accepted for competition.
16.11.1.2    The onus of proof of eligibility shall rest wholly upon the rider or entrant of the machine. Service and parts manual publication dates are not proof of eligibility.

16.15.7 Acceptable machines and components:
All Eras: (this saves repeating a whole lot of stuff for every category)
a) Major Components are: Frame, swing arm, forks, wheel hubs, triple clamps, engine cases, cylinder(s), and cylinder head(s). A machine's era will be defined by its newest major component. (defining the major components is important - it makes the difference between "do I need to use old tyres?" and "can I fit the forks off my 2005 Honda?")
b) Any major component that is visually similar and operationally indistinguishable from the original will be accepted regardless of the date of manufacture. (I am not happy with "similar" - the word "identical" is too strict for minor differences like casting changes, but "similar" is too vague. Open to input on that one!
This bit also replaces the need to specifically allow identical carry-over models)
ba) Any major component that is visually similar and operationally indistinguishable from aftermarket components available in the era, will be accepted regardless of the date of manufacture. (As above)
c) Any modifications to major components must be using principles and techniques that were available in the era the machine is entered in. (just stops loop-holing tactics)
d) Rear shock absorbers will be in the original position(s), using the original mounting points. (As well as avoiding repeating the same thing over and over again, this kills the "single-shock to twin-shock Evo" bike argument dead)
da) Folding footrests must be fitted.
(I killed "exhaust must follow original lines" because it achieves nothing.
I killed the "must meet the noise test" stuff because its already in 16c)


Pre 60 Solo. This class is intended to represent the formative era of motocross. (Weakly worded - needs input from the old hands).
16.15.7.1     The pre 60 class is for machines that closely represent those built up to (and including) 1959 models.
16.15.7.3    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle.
16.15.7.4    Plastic and fibreglass is not permitted.
16.15.7.6     Period carburettors or Amal Mk1 Concentric.
16.15.7.7         Reed valves are not permitted. (Kind of redundant, but added for clarity)

Pre 65 Solo. This class is intended to represent the first generation of purpose-built motocross bikes. (Again, weakly worded pre-amble - input please)
16.15.8.1    The pre 65 class is for machines that closely represent those that were built up to (and including) 1964 models.
16.15.8.3    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle.
16.15.8.6    Carburettors of any type pre 75 round slide may be used.
16.15.8.7         Reed valves are not permitted. (as for Pre-60)

Pre 70. This class is intended to represent the era where 4-stroke machines lost their dominance and 2-stroke machines became dominant. (Ditto)
16.15.9.1     The pre 70 class is for machines that closely represent those built up to (and including) 1969 models.
16.15.9.2     Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle.
16.15.9.4     Carburettors; any type of pre 75 round slide may be used.
16.15.9.5     Reed valves are not permitted.
16.15.9.9    Yamaha XS1 and XS650 engines are eligible.
16.15.9.10    Acceptable follow on models:  AJS Stormer 250;  Greeves griffon models; Yamaha AT1, DT1, CT1, RT1 without reed valve induction. (tightening up the wording slightly)

Pre 75 Solo. This class is intended to represent the last of the short travel suspension era.
16.15.10.1    The pre 75 class is for machines that closely represent those built up to (and including) 1974 models.
16.15.10.2    Front wheel travel will not exceed 178mm (7 inches) rear wheel travel will be limited to 102mm (4 inches) measured at the axle.
16.15.10.4    Carburettors; any type of pre 75 round slide may be used.
16.15.10.5    XS1 and XS650 engines are eligible.
16.15.10.9    Acceptable follow on models pre 75:
    Honda CR125M1, XL250K1, XL350K1, MT250 (all) and MT125 (all)
    Yamaha YZ360B, DT250B,
    Suzuki TS400 (all).

Pre 78 Solo and Women's Pre-78. This class is intended to represent the transition era between the short travel Pre-75 machines and the long travel Evo machines.
16.15.11.1    The pre 78 class is for machines that closely represent those built up to (and including) 1977 models.
16.15.11.2    Front wheel travel will not exceed 229mm (9 inches) rear wheel travel will be limited to 229mm (9 inches) measured at the axle. (I want to change this to 10", but in the spirit of not changing the regs, I have resisted...)
16.15.11.4    Carburettors; any type of pre 78 round slide may be used.
16.15.11.8     Acceptable follow on models pre 78

    CZ 125 1978, CZ400 1978,
    Montesa VB, (ditched the "must comply with suspension limits bit" because the bike has to comply with 16.15.11.2 and 16.11.1.1)
    Yamaha TT500 1978 (is this correct?)


Evolution. This class is intended to represent the era of long suspension travel, before water-cooling, disc brakes and linkage rear suspension became dominant.
16.15.12.1    The Evo class is for machines that use drum brakes, air-cooling and non-linkage rear suspension, as was commonplace until 1981. It also allows for later machines up to (and including) 1985 models that retained this technology. (yes, 1985. Locking Evo into an era kills off the SexMax and any variation of it, without harming any of the 'real' Evo bikes. It still allows the later Evo Huskies, later CZs, and DT175s(!) )
e) Evolution class bikes must have  No linkage suspension, No disk brakes, and Air cooled motors.
16.15.12.4    Carburettors; period flat slide carburettors and any round slide carburettor may be used.
16.15.12.9    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps. (not sure if this is supposed to be on the older eras too? Just repeating what's in the current rules).
f) Front forks must be of the non-USD type, where the fork seal(s) move with the front axle. (stops Simmons USDs and 84 KTM USDs).
(I've written this using Dave Tanner's interpretation which was basically 'we don't care if it came from a linkage/water-cooled/disc braked bike, provided the end result has drums, air and no link'. I don't personally agree, but its the closest we've got to an answer to that long running question, so I used it).


Pre 85 Solo This class is intended to represent the era of the first generation of disc front brakes, water cooling, linkage rear suspension and exhaust power valves became commonplace.
16.15.13.1    The pre 85 class is for machines that closely represent those built up to (and including) 1984 models.
16.15.13.2     Carburettors; pre-85 flat slide carburettors and any round slide carburettor may be used.
16.15.13.7    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.

Pre 90 Solo This class is intended to represent the era where rear disc brakes, upside down forks, and the second generation of exhaust power valves became common place. (by second generation PVs, I'm talking about the multi-element ones like KIPS and HPP, rather than YPVS and ATAC).
16.15.14.1    The pre 90 class is for machines that closely represent those built up to (and including) 1989 models.
16.15.14.2    Carburettors; period flat slide carburettors and any round slide carburettor may be used.
16.15.14.7    The handlebars must be equipped with a protection pad on the cross bar. Handlebars not fitted with a cross bar must be equipped with a protection pad located in the middle of the handlebars covering the handlebar clamps.

(I know sod-all about sliders and sidecars, and there doesn't seem to be much stress around them, so I assume the rules for those are pretty well right?)
16.16 SLIDERS
16.16.1 Slider Frames
16.16.1.1    The frame must:

    Have a conventional swing arm rear suspension with twin shock absorbers,
    Have a front wheel diameter of 23”,
    Have a rear wheel diameter of 19”,
    Have rear tyres with a maximum tread pattern depth of 8mm,
    Not be fitted with leading-link front forks.

16.16.2 Slider Solo Engines
16.16.2.1    The slider engine must:

    Be a single cylinder,
    When four stroke be 2- valve push rod operation,
    Have a single spark plug,
    Be vertical in the chassis,
    Be fitted with a round slide carburettor, or
    Be a period two stroke compatible with class entered.

16.16.3 Slider Gearbox: Classic Long Track
16.16.3.1    The gearbox must have at least two gears.
16.16.4 Slider Sidecar Frames
16.16.4.1    Conventional type frames as used prior to 31st December 1976 must be used.
16.16.5 Slider Sidecar Engines
16.16.5.1    Engines must have been manufactured before 31st December 1976.
16.17 SIDECARS
16.17.1 All Classes
16.17.1.1    Left -hand and right -hand sidecars may compete against each other in Classic Motocross.
16.17.2 Frames and Parts
16.17.2.1    For the Pre-1975 classes, all performance parts except frames must be manufactured before 31st December 1974 and must comply with the following:

        Wheel track measurement, taken between the longitudinal centres of the rear and sidecar wheels must be between 810mm and 1100mm,
        The minimum ground clearance must be 175mm unladen,
        The maximum lean of the motorcycle at saddle height mustbe 50mm,
        The dimensions of the sidecar baseboard in plain view, taken from a line drawn no further rearwards than the lowest point of the front down-tube to the forward most point of the sidecar wheel tyre and terminating no further rearwards than a line drawn at right angles to the machine from the rearmost point of the rear tyre, must be:
            At least 760mm long adjacent to the sidecar wheel,
            At least 300mm wide with at least 25mm radius to all corners.
        There must be no more than 50mm between baseboard and motorcycle and between baseboard and sidecar wheel. The baseboard must be arranged so as not to allow the passenger’s feet to be trapped,
        There must be no less than 4 sidecar attachment points,
        Stirrup fitting for the passenger’s feet are not permitted,
        Handholds:
            Must be finished with a loop of at least 100mm,
            Must not project beyond a line taken with the outer edge of the sidecar mudguard or bodywork,
            Adjacent to the nose section of the sidecar and less than 200mm from the track surface must be at an angle of at least 45° from the horizontal.
        The rear end of the rear wheel mudguard must terminate not more than 65° above a horizontal line drawn through the rear wheel axle and be valanced to baseboard level on the inside,
        The sidecar mudguard must cover at least 135° of the periphery of the wheel and be valanced to baseboard level on the inside,
        No machine may be fitted with scoop or paddle tyres,
        Suspension travel must not exceed:
            152mm (6”) 178mm (7”) measured at the front axle,
            102mm (4”) at the rear axle.
        Rear tyre width must not exceed 135mm (5.3”),
        Brakes:
            Front – single caliper, single disc may be fitted provided they were manufactured before 31st December 1974,
            Rear – rear disc brakes may be used provided they were fitted as standard equipment for that particular combination.

    Only round-slide carburettors manufactured within the relevant period may be used,
    Engine capacity must be up to 1300cc.

16.17.2.2    Pre-1985 is for sidecars constructed with motors manufactured before 31st December 1984.
16.17.2.3    A lanyard operated ignition cut-out switch, operating on the primary circuit, must be fitted to the following with a maximum length of one metre:
DISCIPLINE
   
MACHINE
Motocross    Sidecars
Dirt track    Sidecars
16.17.2.4    Pre-1968 will be for sidecars constructed from road going frames and all major components are those commercially available within the period.
16.17.2.5    The following table sets out the machines and components which eligibility scrutineers may use as a guide in determining eligibility. Entrants must prove eligibility of machines not listed below.
MAKE
   
MODEL(S)
Wasp    All up to and including RT2, RT8 and RT14
Hagon    All up to 31st December 1974
Yamaha    XS 650 all models
Honda    Any K series
Norton    All 750, 850 to Mk2 only
Westlake    All up to 850cc and 31st December 1974
Triumph    All up to T150
CCM    All BSA B50 based models

[Ted]

No reference to Optional B arms in Pre 78?

Another state, another view

[SON]

Good work, well done
And you don't need to borrow a Dickhead Detector,
Not yet

[TM BILL]

Shit Nath you dont mess about  as you have asked i will read properly a couple of times before making any comments .

Thanks for the effort 

[Nathan S]

Son, Bill,  Thanks.

I've had them written in my head for years.
41* and a sick kid have kept me inside, so I guess the planets aligned today.

No reference to Optional B arms in Pre 78?

Another state, another view

Valid point, that I have been struggling with...
I believe the listed carry-over models are bikes that are officially considered to be "close enough" - stuff like the '75 CR125 cylinder, and the DT250B frame gussets & front hub, and the bit where the RT1 uses all pre-70 technology even though it didn't come out until 1970.
If they're identical to un-questioned bikes, then there's no need for them to be listed.
Same goes for the RM-B optional arm.

Maybe there should be a seperate section that lists 'contentious parts' and whether they are accepted or rejected, and why.
There is such a chart on page 7 of CAMS' Production Rally Car regs. The PRC regs are an abomination and the chart always struck me as being pretty clunky, but I see its purpose...

Maybe the best way to handle such things is a formal statement from the CMX Commission?
For example: "The Commission have determined that Part X is legal for Pre-75. Part Y has been determined as not legal for Pre-75" and then include some basic info about how to identify Part X and Part Y?

[JohnnyO]

Good work.. Just had a quick look, I think rule 16.15.7 d) may need altering purely because most of the aftermarket alloy swingarms I have for pre 78 & Evo have the shock mounts in a different position to std for the use of different length shocks.

[VMX247]

Good job Nathan...     Hope you get heaps of good feedback on the input you've written. 

Someone answer why TM250 doesn't get in this follow on list ?

16.15.10.9    Acceptable follow on models pre 75:
    Honda CR125M1, XL250K1, XL350K1, MT250 (all) and MT125 (all)
    Yamaha YZ360B, DT250B,
    Suzuki TS400 (all).

[firko]

Well done Nathan. I'm very happy that you've finally made a start on what I thought you should have been doing instead of offering up silly hypotheticals and empty criticisms. Despite our differences I never doubted your ability to produce sensible rewording of what we've had for 25 years. You can only offer up criticism for so long until those criticisms become empty. You need to offer an alternative  and you've made a good start here........

I'm a bit snowed under with stuff as well as suffering a broken left hand (I'm left handed) so don't much feel like typing tonight. I'll have a good hard read and add any suggestions I feel might be worth consideration over the next day or two.

[SON]

I like The Contentious items list idea

[Nathan S]

JohnnyO, interesting point.
There is a conflict there - it's sort of difficult to define the "original mounting point" on a non-original part - and I had intended that the original mounting points on aftermarket arms would be ok, but it is not obvious.

More thought required.

[Davey Crocket]

Well done Nathan, we've had this conversation before so you know where I'm at.....Alison, 75 TM models not a carry over because the frame is changed and it has more rear wheel travel.