Did it start after you put the K and N in? If so try your stock filter again and see what happens.

 

Probably lean, K&n is the only recent change, whats your outside temperature?

 

did you richen up the fuel mixture after you installed the K&N? if you add more air to the engine you need to run the carb richer to compensate. Sounds like your getting a top end lean out condition. Sometimes this happens to our race cars and we just turn the screws out some and it fixes the problem. IMO

 

If it is the air filter, I would go up 1 maybe 2 sizes up on the main jet. Also raise the needle up 1 notch.

 

the k&N is the most recent change as well as changing to a 250 main jet its about 10-15* C or 50-60*F

 

how do you raise the needle up. i havent done that before

 

250 from what size? temperature shouldn't be an issue, I was worried it was way cold.

 

from the stock 230. no one ever rejetted after it was piped

 

Changing the "E" clip position on the needle, has to do with the timing of when the needle comes off the main jet. This shouldn't have anything to do with wot. Read the plug.

 

i took the head off and the piston and head were black with oil