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Old 04-17-2013, 01:21 PM   #7779
dmcc67
Adventurer
 
Joined: Apr 2013
Location: TEXAS
Oddometer: 10
300 cylinder?

Which 250 won't take a 300 cylinder/piston? I can't find this broken down anywhere.
I have a 2006 KLX250s and am hoping to bolt on a 300 cylinder/piston.

Quote:
Originally Posted by TNC View Post
Mark, mine gained some mpg with the 300 cylinder. At a 250, I had the full Muzzy exhaust...huge head pipe like you describe...modded airbox, and DJ jetting. Still, I had to rev her up pretty well to scoot, which it did OK. With the 300, those other mods probably came more into their own for a performance increase, and I found I could short shift and lug the bike a whole lot more. I think that's where my mileage increase came from.

I also have a totally unsubstantiated theory that the later/current 250 is a tiny bit different from the original 250 that won't accept a 300 cylinder wihtout case machining. I'm suspicious that Kawasaki took the basic 300 model and dropped the bore to 250...marketing, licensing, insurance, and a host of other reasons for a street legal model. When you go back to a 300 cylinder or larger, I'm thinking the combustion chamber and valve layout is more optimum for the bigger bore and therefore provides more/better performance due to being a better "match". One reason I think this is how the valve reliefs are located almost down to the piston ring grooves on the 250. While you can see this occasionally on some engines, it is not really an efficient design for ideal combustion. It seems to me that the power increase of just the 300 cylinder is more than the meager 43cc or so would normally yield. Anyway, just a idea I have about it...worth about .01 cent in today's market.
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