can you go from 13.5:1 to 11:1?

[Hondaexboy]

hey
i was wondering if you have a bike that has a 13.5:1 piston could you replace it with a 11:1 piston? how reliable would a 13.5:1 be ,...would it over heat a lot or anything?
also how much work would have to be done
this is for a 400ex also
thanks

[250X_project]

Yes you could. It may not have quite the power, but would be much more reliable. You could now also run premium pump gas instead of race fuel. No extra work is needed, just rebuild the top end using the 11:1 piston. ;)

[Hondaexboy]

so you would have to rebuit the whole top end to use the 11:1?
how much would that cost about?
thanks

[400exrider707]

Originally posted by Hondaexboy
so you would have to rebuit the whole top end to use the 11:1?
how much would that cost about?
thanks

What he meant by rebuild is just putting in the new piston. You will need a gasket kit too. It would cost you whatever a piston and gasket kit costs. I would say $150 total.

[250X_project]

Yes, that's right. That is pretty much what I consider a top end rebuild, along with a valve angle or lapping job with new seals along with the gasket kit. I would estimate about $125 if you find good sales on eBay, for gaskets, seals, and a piston kit.

I will send You a PM.