I'm about to install the Kawasaki 300cc cylinder/piston on my '06 KLX250S. I have the jetting just about tweaked perfectly for it as a 250, will the displacement increase cause changes to be needed?

Seems like it wouldn't, the engine will just be pulling a bit more air through the carb but it seems logical that the air/fuel ratio should stay the same.

Thoughts/experience?

 

Mine was running a little leaner than I like with the 128 so I went to a 132. I'm at about 500 feet above sea level, stock pilot, open air box, and a k&n, with a two bros slip on.

 

Get the Dynojet kit for the klx300. It has everything you need and instructions.

I did the 300 kit back in January. I actually just got a chance to ride it a couple days ago. it is not a rip roaring beast, but the changes were noticable. I feel like I could now actually pull a wheelie without beating the clutch in first for sure, maybe second. A wheelie in thrid would take some gear changes or serious flogging of the clutch. You will be happy with the outcome