Chain support ( guard )

[Freakshow]

Think this pertains to primary drive set up and acts like a protector against  impact or the like  .....if bolt is damaged or bent, it becomes a tell tail.   This is my take, but then agian I may have it wrong  

yes its fitted on speedway typre motors so when the primary chain lets go the it catches it not your arse.  if they have a completely fitted cover AKA like those steel matchless one then no required but it  its fibreglass or plastic you need a primary bolt catcher.

[Tossa]

2014 MOMS
Section 16D Tech Regs for Classic MX and Dirt Track states:

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

All about the Primary Sprocket nothing about the rear sprocket

[FourstrokeForever]

Thanks for clearing that up Tossa

[firko]

There goes the fresh nickel plating on my 750 and other nickel bikes . If that's the new rule I guess we'll have to comply but that doesn't stop me from being a bit peeved at having to do it. I'll sit down and see if there's a way of mounting it without welding but I'm not hopeful of a neat and sturdy solution doing it that way. If anyone has already fitted a guard to their bike/s could you post some photos to give us a bit of a clue to what's needed and to glean ideas from?

[Tossa]

There goes the fresh nickel plating on my 750 and other nickel bikes . If that's the new rule I guess we'll have to comply but that doesn't stop me from being a bit peeved at having to do it. I'll sit down and see if there's a way of mounting it without welding but I'm not hopeful of a neat and sturdy solution doing it that way. If anyone has already fitted a guard to their bike/s could you post some photos to give us a bit of a clue to what's needed and to glean ideas from?

It only mentions the primary sprocket from what I read Mark nothing to do with the rear wheel

[HeavenVMX]

2014 MOMS
Section 16D Tech Regs for Classic MX and Dirt Track states:

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

All about the Primary Sprocket nothing about the rear sprocket

16.15.4 states drive chains so does not limited it to primaries drive chains
16.15.4.1 is certainly related to primaries as it states that
16.15.4.2 & 3 do not indicate what they relate to but appear to be related to primaries but could also be related to final drives.
16.15.4.4 relates to projecting sprockets and relates equally to primary or secondary drives. the mention of clutches,  frame members and swingarms seems to
                 make it equally applicable to primary and final drive chains.
16.15.4.5 relates to countershaft sprockets which is certainly final drive chain

[Davey Crocket]

Firko, I'm sure with a bit of Aussie ingenuity you could make a clamp system that bolts around the swingarm and you then mount the rear chain guide to it. It wont be hard. Even that homo Lizzie Taylor could do it.

[Tossa]

how perdantic is the writing, so many different ways of looking at it.  All dependent on the machine examiners interpretation.  no clarity what so ever

[Rossvickicampbell]

God forbid - I even agree with Joan - was thinking that maybe something could be clamped rather than welded and bolted more permanent.

Mate - have you finished my header pipe yet    he he he!

[Tossa]

so is the rear sprocket more than 30mm from the outside of the swing arm?

[HeavenVMX]

so is the rear sprocket more than 30mm from the outside of the swing arm?

The lower chain run onto the rear sprocket in most cases would be.

Early in this thread Noel, I think, mentioned that the MA CD commission had recommended the removal of the CDT/CMX exemptions that was mentioned in the minutes highlighted by someone else and that all seems to indicate their intent to require the rear sprocket be guarded. I am not a fan of it either but most people try to present a bike that complies.

You are also correct that it is not bloddy clear if rule 16.15.4 was ment to apply only to the primary drive it should say that and then why mention countershaft sprocket

[Noel]

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQjJjAYMsEgUsEhg6xFjFaFpB0xbbRyH-AjiA4Cm_4bbkA7uiUo
https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcQk4gw0rDqmurbT8EUlbS7bxutvthr3YrlS8GXWNLbuILwVbfLj
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcT17MfFwhcMeueaHa9PZwBofcdnFjN01mSyaMw1ffcAAcPw5aVS

these type of clamp available from boating shops in varius sizes in stainless steel

Have a look at the images section in a google search for split clamps for inspiration

noel

[tony27]

so is the rear sprocket more than 30mm from the outside of the swing arm?

Generally I'd say no but the way it's worded could mean on diameter & then it becomes a yes, official could take it either way

[HeavenVMX]

To make it even more confusing
Rule 16.15.4.5 A counter shaft sprocket which is more than 30mm from the outside of the swing arm pivot must be covered.

Then in every period guidelines from Pre60 through to Pre90 it states that a sprocket cover must be fitted which renders 16.15.4.5 redundant

[Noel]

the wording is "swing arm      pivot"