Hello,I bought new piston with curved dome for my yamaha tzr 125rr ,the old one has flat dome.Cyl code is 4FUOO Y-2 ,cyl head code is 4FUO Y-3.Is this new piton going to be ok?Will it be to big compression?
with a 4fu head it has a mulitaper squish band and the piston domed at the edge is designed to match this, they will be fine used together though if you were to use the piston with a different head i'd imagine you'd run into trouble. the 4fu topend is very nice compared to the other standard top ends it has better transfers and the squish is more technologically advanced
picture of head; http://imageshack.us/photo/my-images/844/18102011022.jpg/ pistons,I think its obvious which is new/old: http://imageshack.us/photo/my-images/72/img2351iu.jpg/
Those transfer ports are huge, any chance of a good set of pics of the transfer ports on the left barrel, the barrel liner is a lot shorter as well, it would be interesting to see the porting differences per barrel, I would be able to mod the standard DT barrel to be the same if I could get my hands on one, time to start shopping me thinks.
those transfers are nice! took me many (many many) hours to cut mine like that to match a 4fu gasket! the piston satelliteone put a pic of up is the kind of dome i meant still flat on top but with the taper on the edge
Ok then.So 4FU setup cant have piston with domed head,right?This may sound crazy ,but could I remove dome with grinder,becouse I dont have time to replace piston.If you want I can take picture of my cylinder.
Edchina NOOOOOOOOOOOO you will thin it too much, I once sanded one down to get rid of a small lump of old piston that had been stuck in the head and came out and got stuck in the newer piston well anyway the thing cracked after not a lot of use because it was too thin.(crack was not where the bit of piston was. Buuuuuuuuuuuuut as with all tuning I do have one thing to say, if you can pay to fix it you can pay to try it.
worked great as a template i put it against a set of split crank cases afterwards and it wasn't far off being flush with the transfer area on the cases as well like that, wore out one of the diamond bits for my dremmel doing it as you have to cut back the liner as well but they are dirt cheep, deffo worth doing if you have the time and patience, the liner comes down further on the standard barrels so gives the piston skirt a easier life than that 4dl barrel in sateliteones picture
