Piston bore sizes

[ben300]

simple question, and im to lazy to look it up, but im looking at rebulding the ex for next season. i want to do a hi comp, 11:1, but i dont want to bore to much if i dont have to incase i need to rebuild and bore again (i dont want to resleave if i have to) and i know there isnt to much help bumpin up in bore size.....

so what i am asking is waht do the Ømm piston sizes corespond to in displacement..

like 85=stock
85.5=?
86=?

....

[Drifterboy3]

If your looking to save money I would suggest just a piston. Unless it is necasary to bore. I know the smallest size is a 407. From what I've heard though is that small of a bore is barley noticeable. I have an 11:1 namura geared 16-38 and I have plenty of power for aggressive trail riding

And 84.95 is stock bore at 397cc
Here are the bore sizes I know of
85.50mm - 402cc
86.00mm - 407cc
87.00mm - 416cc
88.00mm - 426cc
89.00mm - 435cc

[DragonGunner]

Your biggest gain is your compression.....you will notice that more than any bore size. If you got a good bore right now, just have it honed an put a stock bore size 11:1 piston. Personally since you are tearing it down I would go with having it bored to 86mm 11:1

[ben300]

Originally posted by Drifterboy3
If your looking to save money I would suggest just a piston. Unless it is necasary to bore. I know the smallest size is a 407. From what I've heard though is that small of a bore is barley noticeable. I have an 11:1 namura geared 16-38 and I have plenty of power for aggressive trail riding

And 84.95 is stock bore at 397cc
Here are the bore sizes I know of
85.50mm - 402cc
86.00mm - 407cc
87.00mm - 416cc
88.00mm - 426cc
89.00mm - 435cc

ya, its never been torn down. as far as i know. i'm the third owner and i bought it off my buddy. he hardly rode it, and he bought it off an old *** man, who may have rode it 3-4 times. it looked practically brand new when i bought it off him.




Originally posted by DragonGunner
Your biggest gain is your compression.....you will notice that more than any bore size. If you got a good bore right now, just have it honed an put a stock bore size 11:1 piston. Personally since you are tearing it down I would go with having it bored to 86mm 11:1


im leaning towards either the 407 or 416. im gonna be running four gncc's next season in the sport 15+ class (ssshhhhhhhh dont tell anyone;) ) and the PAXC series in C class, unless they get a sport class. i want dependable, all around power. so im definitely going with an 11:1 wiseco and a stage 2 hot came and new valves (im not going to do anyhead work, just stock)....im just up in the air on bore. its starting to smoke a little, so i may have to bore bigger......

[Drifterboy3]

Just because it's smoking doesn't mean you need a bore my cousin just rebuilt his 450r with rincleared valves cleared up his smoking problem. I would suggest a 416 from what I here the 407 is barely noticeable. And I here 416s with cams come close to 450s

[CJM]

The bore of a 450 is much tougher than a 400ex bore. All of the 450s have nikasil coated bores, the 400 doesnt.

Bore size doesnt really matter, compression does. So the next logical size is 402 or 407 and 11:1 piston.

[2001400exrida]

bore size will definitely add some power.