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midlife

Twin shock mods

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How far are you allowed to mod a twin shock before it is classed as a special .

Has anyone be banned, and what with.

PS not talking pre 65 its just bonkers.:wall:

 

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Disc brakes are a big no no ( not sure why). Oversized forks are on the banned list, but I see lots in use, some disguised, again I can't see a big advantage in them. Putting mono engines in twin shock frames has led to problems, I know of RTL engined bikes that have been turned away, but you can convert an SWM to Aprilia Climber specification and that's OK?

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52 minutes ago, teamferret said:

, but you can convert an SWM to Aprilia Climber specification and that's OK?

Not sure there are any benefits in doing this, in fact probably worse than a well set up original motor. Tx and txr are worth swapping, but no major improvement.

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For the clutch & cover as there’s no more ‘88 TXR donor bikes about anymore. (Which I do feel guilty about as the old man was the first to do this back in the ‘90’s) now it’s a well known mod.

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Electronic ignition or maybe a new carb if either is needed, if the footrests are worn out and hanging down then replace them other than that keep it has it is and enjoy riding it.

Why ruin it with unnecessary alterations, you needlessly mention Pre65 while in the same post ask about modyfing a twinshock.

.

Edited by trialsrfun

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5 hours ago, midlife said:

How far are you allowed to mod a twin shock before it is classed as a special .

Has anyone be banned, and what with.

PS not talking pre 65 its just bonkers.:wall:

 

Have a look at the SACU Regs

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My local classic trials Twinshock regs

Machine Eligibility

Twinshocks

1. Motor to be from a motor cycle originally manufactured, produced and sold prior to 1985 as a twinshock motor cycle.

2. Main frame loop to be from a motor cycle originally manufactured, produced and sold prior to 1985 as a Twinshock motor cycle. Replica frames are allowed but should comply with the concept that the finished machine should retain the appearance of the original machine that it pertains to be a replica of.

3. Maximum fork stanchion diameter is 38mm.

4. Fuel must be carried in a fuel tank located above the motor. Fuel lines to be routed away from exhaust and silencer.

5. Rear shock absorbers may be of any type but must be mounted one either side of the machine and must not be mounted at an angle that exceeds 40 deg from the vertical. OSSA gripers exempted.

6. Brakes must be of drum type, no twin leading shoe or disc brakes, and be cable or rod operated.

7. No hydraulic brakes or clutch operation allowed.

8. Ignition cut out switches, kill switches, must be fitted and working. This is a safety requirement.

9. Silencers must be fitted and must reduce exhaust noise to an acceptable level.

10. Tyres to have trials tread pattern and not exceed 2.75 section front and 4.00 section rear. Tubeless tyres allowed. 

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Maximum fork diameter of 38mm means fiddle forks are allowed, what diameter were the last of the Fantic & spanish twinshock forks?

My TY250 works really well with all the parts majesty yamaha sells for the forks now that I have had the top of the sliders bushed to get rid of the wear, rear suspension is laid forward to majesty specs & running a set of rebuilt Fox-shox trials shocks, swingarm has also been lengthened 1 1/2".  Quite an enjoyable bike to ride & still looks period

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6 hours ago, tony27 said:

Maximum fork diameter of 38mm means fiddle forks are allowed, what diameter were the last of the Fantic & spanish twinshock forks?

My TY250 works really well with all the parts majesty yamaha sells for the forks now that I have had the top of the sliders bushed to get rid of the wear, rear suspension is laid forward to majesty specs & running a set of rebuilt Fox-shox trials shocks, swingarm has also been lengthened 1 1/2".  Quite an enjoyable bike to ride & still looks period

The SWM Jumbo came with 38mm forks

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3 hours ago, feetupfun said:

The SWM Jumbo came with 38mm forks

Most regs / definitions for eligibility state max 35mm, except jumbo swm's. It's what's inside that counts !

Edited by b40rt
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