Just installed the 33 on the KLX250 and started it up....had to turn the idle up high to keep it running...given is gas makes it sound fine, but when the RPM gets to low, it starts to make some noises, guessing knocking or pinging...wondering if the 42 pilot is the culprit......knocking and pinging are signs of too lean so i changed the air screw from 2 turns to 1 and then 1/2 and no change.....i dont see anyone using a 42 pilot, so maybe thats too big, yet that would make it rich...should i try a 35 or 37.5 or is there something not right...or do i need more then 2 turns on the screw...suggestions?

 

When the rpms get too low the auto decompression device starts tapping, I'd guess ~600rpm. Probably what your hearing.

Also the screw you are tuning may in fact be a fuel screw, not an air screw, so turning it IN=Leaner. Not sure what mikuni your working with, but if the screw is on the engine side its a fue screw, airbox side it's an airscrew.


You screw setting on hot motor will tell you if you have the right pilot. You need to tune it while running.

 

oh, thanks for the clarification...i got confused because something i was reading was calling it a air jet screw......just tried it at 1/4 and 3 turns out and it still doesnt sound right....the engine seems kinda noisy and the header pipe seems to get hot really fast....i cant see it being lean with a 42 pilot....its the mikuni TM33...i just dont trust running it when im not sure what its really doing