It would be kind've hard to do a bore upgrade without draining the coolant.

 

Oh man! You got me. Wrongly packaged packet. Its past my bedtime anyway.[8D]

 

Hey has anyone here just bored the 249 to fit the KLX 300 piston?

Lee

 

i thought that our engines were the 300, except they just had a sleve in it to make it the 250? pop the sleve out and get a bigger piston?? i'm not really sure, garenteed nobrakes or someone else will have a solid answer

 

Stock carb, stock needle(no more washers to lift it), twin-air filter, moified air box lid w/ filter skin, 135 jet, 40 pilot, 1-1/4 out. At sea level, its lean as as can be, but smooth and torquey. 45-50mpg

I find a very strong low to mid range, but lacks the zip it used to have at at 9-10k rpm in the upper gears.

 

The 250 cylinder has larger water jackets than the 300cyl. Boring and re-plating the 250 would be best for a 300 upgade. Going from 250 to 331 requires a sleeve, due to the larger water jackets. A 300 to 331 is no big deal.

 

Not sure I agree with that. Therehas to be agood reason why that isn't being done. My guess is, just like a car, boring too much will result in too thin a cylinder wall, possibly getting too close towater or oil passages. Don't quote me on this, just throwing out a doubt !

 

The KLX250 cylinder needs to be bored out & replated or install a sleeve to make it into a 300 or into a 330 it isnot a sleeved cylinderin the stock form.

 

It is not worth boring and replating the 250 cylinder to 300. By the time you pay someone to bore it and then have it re-niskal plated you might as well just buy the 300 cylinder to begin with. If you want to go to 331 for less money than send your cylinder to Bill and have him bore it and then sleeve it to 331. He can also sleeve it to 300 but it will cost about the same and would be dumb not to just go to 331.
No the 250 cylinder does not have a sleeve that can just be removed to go to 300. It is a different cylinder than the 300 and is also niskal plated, no sleeve. Remember in mostcountries other thanthe US the250cc version klx never saw a stop in production.
As far as pumper carbs are concernedI am sure taking the klx to 331 with the stock carb is a major increase but I read some where that a klx300 with a pumper will out preforma klx331 with the stock carb. But this all depends on what type of riding you will be doing. If you are going mostly street I would go 331 with the stock carb. If you are mostly dirt, get a pumper.

 

Mileage sometimes doesn't make sense. The klx, bumped to 300 like described, gets 45-50mpg? My 1200cc Buell gets 50mpg. Makes around 85 rear wheel horses/100+ at the motor. It doesn't seem fair; the KLX should get more mileage! Heck, one of the guys at the local shop has a tricked Hayabusa he dragraces, and it gets 40mpg when he's cruising and not on the nitrous...very aerodynamic though in comparison!
doc