I see alot of guys have bolted on a 300 cylinder- has anyone just bored out the stock and dropped a new piston in??? haven't heard much about this. Wondering how this would effect reliability etc. and maybe it is not as good as factury parts?? thoughts

have a great weekend

 

Mike, as far as I know, there is only one person that has sleeved a 249cc cylinder and bored it out to 331cc. Marty, a guy that used to post regularly on this board, is in the process right now of breaking in his new 331cc parts. He employed the services of Bill Blue to do the machining on a 249cc cylinder that he got from Nobrakes. While he has not gone full throttle on it yet, initial indications are that this route to Big Bore Heaven is a viable one (and quite a bit cheaper than any other route for that matter).

 

If you would like to get an impression of a bored-out 250cc jug, visit www.krlworld.com and go the sub forum called 'your klx' from there, go to the 'KLX engine' section and see what Marty has done so far. He had a 250cc jug bored out to 331, complete with steel sleeve. All machine work was done by a fella named Bill Blue, who does outstanding work. He's got the same, wonderfully forged JE piston that is used in the kustom Kraft product. Marty has also fitted a pair of Yoshimura racing cams to his little fire breather and willprobably put it on the dyno sometime next week to give us all an idea of what's possible from this bike at stock compression.

I will agree with what Iowa said though. If you cangetgood deal on a KLX300jugon ebay, then send it to Kustom Kraft, that would be the ideal situaton. However, with more and more people going to the 300cc jug, there should be a lot of 250cc jugs becoming available for dirt cheap. For about $400.00 more you can haveit sleeved and bored 331(parts AND labor), so it's just another option that's available.

 

thanks for the info--

tremor- jsut curious- what are you doing over in Japan??? if it is in service of our country- I thank you.

 

I came here while I was in the service, retired here and am working for a defense contractor.

 

i dont know the answer to this question and im curious.. would boring our stock cylinders .03 over really remove that much meat that the cylinder strength would be sacrificed? i understand that once bored ur pretty much done for anything else if you scratch the cylinders but im just skeptical that theirs that thin of walls in it stock.. could be wrong tho.
by the way... what would .03 over make our bikes?

 

Not sure what you mean, jsac. Do you mean .03 inches larger diameter? That's not much, less that a millimeter. The stock piston is 72mm for the 249cc and the 292cc (300 kit) uses a 78 mm piston, while the 331cc uses an 83 mm piston. I've had both the 292cc and 331cc and while 292cc is good, 331cc is just more of that good clean wholesome goodness.

But to calculate the displacement, the formula is PI * r * r * stroke where r is the radius or 1/2 the bore or piston size. PI is 3.1415 ...

 

whats the "general" amount done to punch a cylinder mildy? i was always hearing friends sayin .03 over.
i have no idea as to what standard of measurement they were refrring to.. i was guessin standard.

 

You might bore a cylinder "30 over" (30 thousands of an inch) to bring new life to an old engine...
But with our KLX we're talking some serious metal removal... Like nobrakes said - 72mm to 83mm is quite a jump in bore size... Almost half an inch!
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