Suzuki RL125 sort of...

[cyclegod]

I have a dark idea lurking in the back of my head it involves turning a TS125 (74) into a trials bike by doing the following...

1,  Change the gearbox to a TM125 close ratio but keep the low 1st gear from the TS
2,  Fit a narrow tank from the later 78-79 TS100/125
3,  Use a TM125 swingarm (no holes drilled through it for passenger pegs like the TS has)
4,  Trim unecessary lugs etc from frame and use TM alloy tripple clamps
5,  Mount foot pegs 2" back and 1" up to be about 1"-1.5" below swingarm pivot
6,  Use universal trials seat/guards etc
7,  Use longer than stock trials shocks (will steepen steering a little)
8,  Trim back the steering lock lug to safest minimum (no dents in tank etc)
9,  Create exhaust box and header like WES does for TY's (route through frame where applicable)
10, Machine head for better compression but start off with stock barrel and carb (24mm)


Am I mad or has all the fiddling with TS/TM internals and externals lead to some reasonable inspiration?

[TT5 Matt]

check out a tc125 barrel pritty sure they have a smaller not as high exhaust port compered to the ts,abit like what they do on the er185 verus tf185 aggie bike.

[DR]

Sounds like a plan CG. I was only speaking to someone else harbouring near exactly the same plans a few weeks back Matt, the TS and TC125 share the same cylinder and porting

[tony27]

The normal thing to do with footpegs now is get the bottom roughly level with the bashplate, helps out a lot with balancing. My TY has the pegs mounted like this, front of the mount is about in line with the back of the swing arm pivot. Almost seems easier to balance than my modern bike
Sounds like a interesting project

[David Lahey]

Footpegs set at bashplate height on a TS125 frame used for trials will mean that the riders bum will cop a hammering riding obstacles unless they are extremely tall. Trials frames are much shorter between seat rail and bashplate than Trail/MX bikes.

[David Lahey]

Why use the TM gears for ratios 2345? Surely the TS gearbox will have a wider range between 1st and 5th?

[cyclegod]

Why use the TM gears for ratios 2345? Surely the TS gearbox will have a wider range between 1st and 5th?

If your final gearing is trials suitable then the TS gear ratios would mean that 3,4,5th gears are almost never used (unless you like trials at 100km/h plus  )
The TM125 2-5 is much more suited to the trials application  if second is what you would normally use as a low gear, first would be for creeping along between 0-5km/h. It is actually an easier mod to do than to try and use the whole TM gearbox.

[cyclegod]

Actually....come to think of it... I could do all this to a TS185 as well....

[huskibul]

    How does the RV-125 compare to either TS or TC in both gearing and port configuration ?,ive had an rv motor sitting in the shed for age's ,with the idea of maybe one day going along the line's of the Gaunt or Mclaren/suzuki  ::)oneday

[David Lahey]

Why use the TM gears for ratios 2345? Surely the TS gearbox will have a wider range between 1st and 5th?

If your final gearing is trials suitable then the TS gear ratios would mean that 3,4,5th gears are almost never used (unless you like trials at 100km/h plus  )
The TM125 2-5 is much more suited to the trials application  if second is what you would normally use as a low gear, first would be for creeping along between 0-5km/h. It is actually an easier mod to do than to try and use the whole TM gearbox.

I'm suggesting to use the complete TS gearbox not the TM gearbox.

[DR]

sounds like a lot of work for nuthin'! The standard TS is a great bike for trials without any mods at all..just ask Bill


witness the trials grand master at work

[JC]

CG,

I've been seriously pondering almost the same thing lately, but an RL 185/200 instead, & was talking to Doc & feetupfun a little about it a few weeks ago.

Why? Cos I've accumulated a fair bit of 185 stuff almost for nix, my interests are turning to trials & I'm on a tight budget

Here's what I've found so far:

TS185 engine & std 24mm carb appears a good basis for trials engine (longish stroke, mild porting & reasonable gear ratio spread).

TS185 frame is hopeless for trials: too long, too deep (seat rail to bottom frame rails 17.5", whereas typical trials frames are 16-16.5"), poor ground clearance, motor sits way too far forward (30mm gap between engine cases & pivot tube) but can't easily be moved back, & hopeless brake pedal arrangement.

TS125 frame is much more compact for trials (seat rail to bottom rails apx 16") w good gr clearance, good brake pedal arrangement, shorter w'base, & motor sits further back, but maybe a little short in the cockpit (depending on one's height/size) & 1310mm w'base is still a little long & 30deg rake a bit much.

TC125 1st gearset could be used (I think) to close up gap to 2nd gear a little (from 34% to 26.5% which is fairly typical of trials bikes), but is not as low a ratio (2.47 vs 2.75) & reduces overall ratio spread (from 3.44 to 3.1)

I have an article on a Gaunt modified TS125J from 73 if you want a copy

Found elsewhere that RV125 barrel has milder exh than TS125 (open 82deg BBDC instead of 87deg) & smaller inlet

So here FWIW is what I planned - sort of a parts bin special that Suz could have built circa 71-73

73 185 engine w std 24mm carb
Probably std TS gearbox internals but reduced 2ndary reduction
TS125 frame
TM125 tank
TS125 or TM125 kickstarter (to clear rearset f'pegs)
Softer fork springs
Footpegs to be rearset to be about 14" from rear axle & raised a little above bottom frame rails
Longer shocks &/or laid down a little to reduce rake
Shortened brake pedal, minimal seat & decent bashplate
Perhaps rear mudguard loop bent up a little
21" fr wheel, tho may try std 19" 1st
Completely refabricated exhaust w trimmed head for clearance

Options include:
Triples w larger offset (later TS?? or TM) to reduce trail, but this increases w'base so perhaps also derake frame by lengthening the backbone (more room in cockpit) & bringing back the fr axle for shorter w'base
ER185 33mm forks & triples or TL250 forks & triples (cos I have a set) which would need the deraking
Heavier flywheel
66mm piston
Widen exh port perhaps

[cyclegod]

Having just completed my TS185 powered TM125 I was leaning toward a 185 powered TS125, but it's early days yet my TM-S started with just a frame and some grand ideas. I figure that as things stand it would take me 2-3 years to have a sorted ride-able bike on my hands and a year of that would be spent nutting out the details of how? why? and where? changes need to be made.

[montynut]

Most trials 2 strokes do not have long strokes. You would think that would be the case but not in practice.

TY250 same bore stroke as DT and YZ of the era
TY175 same piston, crank, cylinder as DT175 of era
Montesa Cota 349 bore 83.4 stroke 64mm and this engine is recognised as one of the best luggers around
Montesa Cota 242 bore 70.5 stroke 61.7
Bultaco I believe are the same as pursangs of the period (will stand corrected on that)

What they all have are very heavy flywheels. The Cota 242 has a 3Kg flywheel plus a second flywheel on the crank primary drive gear. They also have relatively small carbies. The TY175 has a 22mm? I think while the Cota 349 & 242 have 26mm.

The exhaust system on most Trials bikes have long straight (constant diameter) headers with expansion /baffle boxes mid then a final relatively restrictive silencer. The Cota 242 was the first of the Montesa bikes to have a true expansion chamber type exhaust which is very long slow expansion front cone long mid section followed by a relatively short reverse cone, long small diameter stinger with two silencers.

The chassis needs to be short wheel base (small turning circle). Have you thought about maybe a TS185 engine in a TY175 frame or copy the TY175 geometry with more ground clearance as that is the only TY175 handling shortcoming if there is one.

It is most unlikely that you will use other than 1st, 2nd and possibly 3rd on a very odd occasssions in twinshock trials so only concentrate on those. Remember that a very large rear sprocket is a real pain as it hit everything when in section and bends or derails the chain or stops you dead. Better to have the lowest internal gearing possible.

Just some thoughts. Dave (Feetupfun) is the oracle for all things trials and what he hasn't done or doing he knows who is.

[JC]

Most trials 2 strokes do not have long strokes. You would think that would be the case but not in practice.

What they all have are very heavy flywheels.

They also have relatively small carbies.

The exhaust system on most Trials bikes have long straight (constant diameter) headers with expansion /baffle boxes mid then a final relatively restrictive silencer. The Cota 242 was the first of the Montesa bikes to have a true expansion chamber type exhaust which is very long slow expansion front cone long mid section followed by a relatively short reverse cone, long small diameter stinger with two silencers.

The chassis needs to be short wheel base (small turning circle). Have you thought about maybe a TS185 engine in a TY175 frame or copy the TY175 geometry with more ground clearance as that is the only TY175 handling shortcoming if there is one.

It is most unlikely that you will use other than 1st, 2nd and possibly 3rd on a very odd occasssions in twinshock trials so only concentrate on those. Remember that a very large rear sprocket is a real pain as it hit everything when in section and bends or derails the chain or stops you dead. Better to have the lowest internal gearing possible.

Just some thoughts. Dave (Feetupfun) is the oracle for all things trials and what he hasn't done or doing he knows who is.

Yeh Monty, we have noticed what you point out. Many trials bike engines are short stroke due to manufacturing economics/constraints - eg using existing engines, can't fit longer stroke in existing cases etc. TS 185 engine is good bore/stroke ratio in my book - much better than TY175

Likewise w heavy flywheels, but std TS185 is hardly a snappy engine - its pretty docile. Dave told me he actually started his trials riding on a stock TS185 & said it was a pretty good trials engine - better than TY175 engine (IIRC)

And yeh, I have considered a later model TS185b/c engine (w centre port exhuast) in a TY175 frame, but Suz engine is a fair bit longer. Not an insurmountable problem I know, but while I'll modify a trail bike frame no worries, I'm not so keen on modifying a good trials bike frame & I don't have a TY175 frame anyway. Copying its geometry aint a bad idea, but it be difficult to get a TS125 frame down to 1260mm wheelbase. I figure if I can get down under or close to 1300mm it'll be a good start.

It'll be a work in progress & one can think of plenty more options to consider.

The idea is for a cheap fun bike using stuff lying about unused & a bit of aussie ingenuity, that'll be reasonably proficient at feet up fun