kawasaki 650 jetting question

[randrew20]

i have a 1988 kawasaki 650sx jet ski that i believe might be jetted wrong. it has an engine out of a 1991 kawasaki X2. the original sx had a CDK card and the X2 engine has a CDK2 carb. i have a stock exhaust and intake and the engine is stock. the carb is currently jetted with 140 High and 85 low jets. It seems that the top end isnt quite what it is supposed to be. the ski does not have much more power after about half throttle. I had a X2 a few months ago with the same engine and it just seemed alot faster. I was told that i need a 125 jet in the high speed but i dont want to lean it out and fry the engine. so i was just looking for some advice on what to do and what size jets i should try if the 140 is not the right one. i would also like to know if i get a K&N air filter will i need to rejet the carbs or should i leave them the same?
thanks,
Ryan

http://www.justbuytickets.com