I have an 89 Fourtrax 250R, the bike is stock with the exception of a Boyesen Reed cage and a CT pipe. I recently removed the airbox and I am running an open air filter setup.

My question is what should I change the jetting too? I have 165, 170 & 190 jets, all of these dont make the bike run right. I also forgot what the plug color should look like to see if it is jetted properly.

Any help would be greatly appreciated.

 

What is your elevation? I would think that 165 is the closest but still a little big. Try a 160.
ERIC

 

My elevation is usually sea level, but no more than 500ft above.

Should I go by the color of the spark plug in order to determine that the 250R is running properly?