I bought my 09 ninja this year brand new. Its my second bike i had a yamaha yzf600r before and I downsized because well i got too many speeding tickets!

1)I bought a k&n filter
2)full yoshi carbon fiber exhaust
ran ok after those two then installed dyno jet kit...and it went all down hill from there!

installed 98 jets i think. Started ok after wards, next day wouldn't start. bought new plugs. now starts but i need to give it hair of gas so idle screw is messed up. both spark plugs have spark. but it sounds like one piston isn't firing because the exhaust doesn't sound the same. so i tried the header touch test. one header is hotter than the other. and now idk what to try next...Please help me out!

 

Congrats on the new ride. An 09 250? or the 650 twin? You will need to re-jet the bike with that new full exhaust system and filter.

Keep both pilot screws the same. 2-1/2 maybe 2-1/4 turns out from the seated position. (just a generalized starting point) This is for the idle or slow speed circuit. ( You installed a kit, so you would have checked the needle positions on assembly and verified float heights, also verifying that the CV diaphragms are not pinched or not set correctly). If you are comfortable with the install and checks, generally start with the pilot screw adjustments first for low speed issues. The existing plugs should be fine for such a new ride. Also verify that all vacuum lines are back in place and are not pinched.

Welcome to KF

 

Start by junking the Dynojet kit and refitting the original jets and needles.

Rob

 

Welcome to the forums.