September 7, 20169 yr I can answer that one b40rt. Wiseco pistons expand more with temperature rise than original Yamaha pistons. The extra heat created while new rings bed into a fresh bore can take the piston temperature (size) to the point of being at risk of piston-to-bore seizure, more so than with the lower expansion rate Yamaha piston. Of course as well as the way the break-in is done, the risk of piston/bore seizure also depends on what clearance the rebore was done to.
September 7, 20169 yr Cheers Feetupfun, just put one in a Rotax motor and it got hot quickly as you say. Has about 3 hours on it now and sounding / running really well.
September 10, 20169 yr Right on with the details David. When I have a rebore done on one of my TY with Yamaha piston , I usually ask for a .002 inch clearance and I do the running in over 2 days : first morning, start and run for about 30 sec, and in the afternoon, start and run until I can feel the heat on the cyl., let it cool and repeat. The next day I repeat but i run it longer. I know it's over over overkill but I had one done ever 10 years ago that has not started to rattle yet. Guy
November 5, 20169 yr Here is a photo of the next project when I finally get round to building it as it has Been under my bench for a few years now. Its got the shortened inlet mod and a new pink mudguard which I purchased from Ctc.
November 5, 20169 yr my 1977 ty250. I am pulling it apart to refresh it. That's in way better nick than my current old nail of a TY, but it still goes so well I can't be bothered to do anything to smarten it up.It was out today on firewood duties,being thrashed around in the mud by my son.
December 27, 20178 yr My two '84 250 mono's... 'Ol Blu and 'Ol Yeller... Edited December 27, 20178 yr by thai-ty
January 4, 20188 yr My son (15) on his TY - second in experts in his class in the Kia champs last year ????
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.