KR-1S.co.uk Forum

hello everyone

I need new pistons.
i want to buy new Mitaka piston.
these are available from 55,94mm - 55,97mm.
what is the best piston clearance?
is ok 0.05mm or 0.06mm better?

Regards
Dirk

I always get mine honed to 0.05

Thanks for the answer.
i asked because at Yamaha (2MA) is 0.05mm too tight (with ProX Piston).
the cast iron liners need to 0,065mm.

pistons are ordered, and I hope the KR is ready for use again this month!


Dirk

Ah I see the difference, 0.05 on the nicasil plating is good and what I always request.

dirk wrote: the cast iron liners need to 0,065mm.

normaly clearance depends on the piston no ? forged vs cast. forged needs slightly bigger.

and where on the piston do you measure? of course front to back but
do you average the clearance because between crown, gudgeon and skirt...
the difference between those alone is 0.05mm let alone from empirical measurement (repeatability)

good morning

i measure it at 25 mm from the skirt end.
the Yamaha manual says between 0.05 and 0,055 mm.
this is too tight with ProX!
i have tried it twice....
with Yamaha Piston it works.
perhaps PROX Piston expand more?
both are cast piston.
at the RG500 is 0,065 - 0,075 mm standard.

Dirk

Don't forget the RG400/500 have iron liners so assume more clearance?