i need experienced engine builders

[trx400EXtreme]

lets say that i put in a high comp piston in my 400ex. are different valves or anything besides the piston, rings, and gaskets required. i really want more power but don't want to have to rebuild the whole motor. i just want to throw in a piston. i just need to know what ir required to keep the reliablility.

[86 Quad R]

in all honesty i would suggest that you get the service manual and follow its proceedure. it will help guide you through the process. there are things that need to be checked when redoing a top end. :cool: there's a bit more to it than just "throwing" in a piston. :p

[Ruby Soho]

you can just put a piston in without needing anything else. you may want to though, such as a cam at the very least

[wilkin250r]

If you're looking for more power right now, you'll still be looking for more after the piston.

A high-compression piston will certainly give you more power, but it isn't a ton. There really aren't any single modifications that give you huge power gains all by themselves, it's usually a cumulative effect from a combination of modifications.

Me, personally, I would never bother with the hassle of tearing into the top end without changing/upgrading several components. The piston and a camshaft at the very least, possibly a big bore (depending on my desired power delivery). If I could afford it, I'd also get some porting done. But I wouldn't bother for just a piston all by itself.

[pro-rider46]

if you can. get a wiseco 440 kit, and have someone install it. they are only like 400 when you add it all up, and get it ported. that should set it up well.

[TRXRacer1]

Spring for another $65 for a bore job and go to a 416. If you still feel like a little power is needed you can easily do a cam later.