Boring out 250cc?

[crackerjac]

I have the crf230 Zong clone, 65.5mm x 66.2mm bore and stroke. There are a number of big bore kits for the CRF230 but I was wondering if anyone has bored out to 67mm and ran the much cheaper off the shelf 67mm piston? it would only be about 233cc but still it a jump over 223cc. It would give it a bit more compression as well but nothing crazy.

[jimwildman]

Originally Posted by crackerjac

I have the crf230 Zong clone, 65.5mm x 66.2mm bore and stroke. There are a number of big bore kits for the CRF230 but I was wondering if anyone has bored out to 67mm and ran the much cheaper off the shelf 67mm piston? it would only be about 233cc but still it a jump over 223cc. It would give it a bit more compression as well but nothing crazy.

do you mean a cg250 push rod engine? thats not at all like a crf230 engine. Its a clone of a honda nx150 with a big bore to 230cc.. If its the overhead cam version I couldnt say im unfamiliar with that version of the chonda clone. That said being based on a 150 its allready pretty much oversquare, you could deck the head for a bit more compression but its allready under stress, so id be afraid of making it less dependable.

[crackerjac]

Originally Posted by jimwildman

do you mean a cg250 push rod engine? thats not at all like a crf230 engine. Its a clone of a honda nx150 with a big bore to 230cc.. If its the overhead cam version I couldnt say im unfamiliar with that version of the chonda clone. That said being based on a 150 its allready pretty much oversquare, you could deck the head for a bit more compression but its allready under stress, so id be afraid of making it less dependable.

No I'm refering to the OHC version that is a copy of the CRF230F. Same bore and stroker and case basically.

Anyway, since posting this I did some investigating and found out that it could easily be upgraded to an off the shelf 67mm piston for a fraction of the cost (under $100) of the kits BUT like many have found that have done the conversion to the CRF230 it leaves the cylinder walls a little thin boring them to 67mm so depending on the type of riding you do it can reduce the longevity of the motor a lot. So you have to decide if it's worth the extra CI for the reduced life of the motor.