Hi i have just bought a suzuki rm 250 engine, it is a 1985 one and has no power valves, i would ideally like to have power vavles, if i could find a piston casing from a more modern rm 250 motor and replaced it for the one on the engine currently, would it work?

Thanks
Roy

Hmm - I guess nobody knows. I wouldn't try it without a lot of measuring. Would it not be easier to swap out the engine whole, if you wanted powervalves? After all, it's not exactly going to be all-original any more...

Or even look out for the bike with the powervalves and upgrade - do they really make that much difference to a 250 though? What ARE powervalves? Isn't it just some kind of descrption Suzuki thought up to make it sound more powerful? (like the way it said 'Energy Induction' on my baby Yam).

Personally I wouldn't try fitting bits of different engines together without a fair amount of knowledge and experience - and if I had the knowledge and experience it would prolly tell me not to do it!

Aren't they exhaust valves that change the back-pressure from the exhaust system? That rings a bell (though I'm sure others will be able to explain it exactly). I think the valve stays closed at low revs to keep the back-pressure high, and to help keep the power up. When the engine's racing away, the valve opens to let the exhaust flow more freely.

I *think* that's the deal, anyway. From that, I would expect the head of the engine to be very different to the non-powervalve unit. If the newer head can be mounted onto the older engine block, you might get away with it. But then has the later motor been beefed up / rebalanced / otherwise tweaked to make sure the powervalves don't tear it apart, or cause too much vibration.

Best bet would be to find the powervalve engine and compare it very closely. By that point, though you might be as well swapping engines entirely as I said before.

Yeh after this post i looked further into it and a power valve engine and non power valve one are quit different because the later engines from 1986 onwards used mechanical power valves that are controlled by small sprockets in the engine casing that are in turn controlled by the throttle, so it will never work. Even thought this engine does not have them i think it will be quick after its had a good rebuild.

Thanks
Roysten