Trials engine cradle

[ian640]

Interesting - I've already got my TFS footrests quite a way back, about in line with the front of the rear tyre. I haven't particularly felt that the front end is heavy - I have tele forks and standard full width British Hub. There seems to be quite a lot of scope for moving the engine further back though. Please let us know if it makes a significant difference.

Cheers,

Ian.

[Liam Robinson]

Sounds like your tfs is similar to what I have done to mine as my footrest are in the same position. I guess it depends on how far you want to go in modifying your bike on wiggy's tfs he moved the engine right back to just in front of the swingarm bolt and cut the bottom of the gearbox for more gound clearance it definitely looks the part though.

[Liam Robinson]

Finally got the cradle in the bike just need to finish the bash plate.

[teamferret]

Looks well smart

[teamferret]

Matter of interest Liam, how much flywheel weight are you running? I'm building up a lightweight short-stroke engine at 210cc and will start off with the motosplat set up with virtually no flywheel weight.

[Liam Robinson]

210cc short-stroke sounds like a great idea as there are loads of the 9e cranks around. Is 210cc the max u can get out of a 197 barrel? Anyway im running 3.5kg flywheel you can got heavier but i can't see the need.

[PeterJGreig]

I have a circa 1919 Hobart with a Villiers 269cc engine which has an external flywheel approx. 10" od. and of appreciable weight. The amount of low revs plonk is amazing (no clutch so slow speed riding to wait for traffic lights to change is essential!) I have often wondered if such an engine in a trials bike would work.Peter.

[teamferret]

A huge flywheel would work, I think, on most sections, but quite a few require almost explosive acceleration which the flywheel would surpress. Also some notably rocky sections require speeding up and slowing down in little distance travelled. Probably best suited to the easy route.

Liam, the 197 crank has the same stroke as the 250. I'm using the crank out of a 2L which was 175cc. The kart people used a 1H (63mm) piston or an oversize but I'm using a suzuki TS185 item at 64.5. Waiting on the barrel to come back from 'plating' as I used an aluminium liner to keep weight to a minimum and help engine cooling. I also only intend using one ring on the piston, taking advantage of the smaller clearence I can run with this type of bore.

[Liam Robinson]

Sorry I meant the 5 1/4 rod as most run the 5 1/2

[Liam Robinson]

Finally finished cradle and bash plate. Very pleased

[teamferret]

Fabulous, looks well sorted

[ian640]

Finally finished cradle and bash plate. Very pleased

That looks great - well done. Did you go for a steel cradle and alloy bashplate in the end?

[ian640]

A huge flywheel would work, I think, on most sections, but quite a few require almost explosive acceleration which the flywheel would surpress. Also some notably rocky sections require speeding up and slowing down in little distance travelled. Probably best suited to the easy route.

I have a 4kg flywheel in my TFS. It certainly smooths things out but I miss that switch-like acceleration you get with a modern trials bike. That said it gets up most obstacles if you rev it hard enough to start with, it's just that a lot of advance planning is needed.

[John Wakefield]

Thats why Bultaco & Montessa saw off Greeves with their short stroke engines with small diameter flywheels

[Liam Robinson]

That looks great - well done. Did you go for a steel cradle and alloy bashplate in the end?

Hi Ian yes went for 3mm steel then a 4mm removable alloy bash plate. Already thinking of what to do with the next one . On the flywheel weight side I know that electrex world do a 6ish kg flywheel but it's a lot of stress on the bearing