Topic: race pistons

[Colin Tweedie]

Got a 500/4 engine to rebuild and tune can anybody recommend which pistons I should use ( I was told CG pistons fit ) I would also like to do some work on the crank but not sure how much to shave off any help tips greatly appreciated

[turboguzzi]

edit as i see that you do race in scotland

go for stock pistons, head/block milled 1.6mm, pistons edge turned with a 15 degs slope to match the combustion chamber chamfer.  bump in compression will be notable, its simple and cheap to do. did 1.5 seasons like that

XL125 pistons, you will have to turn down the crowns as CR will be too high

Davies motorsports in UK were working on producing dedicated 500 race pistons last time they were seen

no easy solutions, the days that yoshimura made race pistons for the cb500/4 are long gone

[Jim F]

CP out of California makes an excellent piston but expensive

[specweld]

S.E.P. in Kegworth will sort the crank for you Col.

[classic bike tuner]

take a look at this topic   you find olmost everything

http://forums.sohc4.net/index.php?topic=63228.0

[Colin Tweedie]

1.6mm  seems an awful lot?  Do you have to  machine the valve pockets as well to avoid the valves and the pistons colliding.  Where can I get a race cam in UK

[turboguzzi]

will have to check my numbers again but it was about it, 1.6-1.2 and yes, pockets were deeper also because of the megacycle 126-20 cam . if you feel uncomfortable about so much milling, then go with XL125S pistons but these will require crown lowering as well as re-pocketing...