Bought my twinshock ty250 off Ebay back in the summer,lovely looking bike - shot engine.No problem,I thought - have it apart and do a full rebuild and then I'll have a reliable bike that I can ride for a few years with no worries.Built it up with new mains,seals,big end,rod,small end,bore to +1mm,piston + rings.

It rattles,more than I think it should.What I would like to know is are there any special tricks to stopping it rattling.The parts came from Hursts, the barrel was bored to the bottom tolerance and I spent a long time with swiss files on the ports making a good radius on each edge.I built up the crank and straightened it to less than 1/2 thou on both sides.

i have put rubber blocks in the fin gaps in 2 rows up each side of the barrel and across the head.The rattle is only at and just above idle - with a few revs on it shuts up and sounds good.I have done 3 trials on it now and it runs beautifully -apart from the rattle.I dont really want to take it apart again,but I will if I have to.It has shown no signs of nipping up,I know they are a rattly old aircooled motor,but others I have listened to have been much quieter.I did the mods to the piston that Hurst's told me to,wondered if anyone is using Wiseco pistons.

I used a 0,5mm oversize Wiseco in a rebore 3 years ago of my TY250 twinshock and the piston has been nice and quiet mechanically at all RPM ever since. I haven't even bothered to fit the rubber blocks to the fins.

Thanks for that,I dont suppose there is much point in asking you where you got it from,as you are in OZ,but then again I'll be out there in Feb,(WA tho) and i could pick one up then.Havent had much luck in finding a stockist here in the UK.

Have you tried to adjust the slow running mixture as I have noticed that on my TY175 it does make a difference to how quiet the engine is on tick over.

Cant say I have,it has always run so well,(apart from the noise) that even after the rebuild I didnt think it needed any adjustments - I'll have a fiddle with it at the W/E and see what happens.

Thanks for that,I dont suppose there is much point in asking you where you got it from,as you are in OZ,but then again I'll be out there in Feb,(WA tho) and i could pick one up then.Havent had much luck in finding a stockist here in the UK.

I bought that WISECO piston kit from my local (Gladstone, Queensland) Yamaha dealer. I'm sure any bike shop worth it's salt in OZ could get WISECO piston kits.

An alternative for you would be to buy one from the US (say from B&J Racing). For us here in OZ the total cost of some items from the US is quite competitive with local supply due to the low freight rates from the US.

Edited November 22, 200619 yr by feetupfun