2006 YZ450 hesitation, stall

My bike is completely stock except for richer jetting. I think my carb needs a modification. When I go to exit a corner sometimes, my bike hesitates, pops and then stalls. My jetting is a little on the rich side with the 170 main and 48 pilot. I believe the bike needs more of an accelerator pump shot. I noticed that there are different bowls and other items available. What do you guys recommend that I do first?

First, check the pump timing per the manual.

If that does not address your problem, try the O-ring mod:


If that works out, consider removing the O-ring and replacing the accelerator pump actuator spring with one from Merge Racing.

Although the AP leak jet is not actually intended for trimming the AP output, it can be used for that. Oft times when running a boosted AP, it's necessary to use a larger leak jet to reduce the amount of fuel delivered.

The add-on float bowls are a massive waste of money. The leak jet will very rarely ever need to be changed or adjusted after you get it right, and the bowl itself accomplishes nothing. Merge makes a pump cover with an adjustable leak jet, if you must have one, and costs half as much. Still, not really needed.

If, after you've got the AP timed, etc., you still feel like you need it to improve, send the carb to Zip-Ty and have it modded for about $130. Greatly improved overall "sharpness" and response.

Your jetting is on the rich side. WHY??? Got back to stock on the main and down to a 45 pilot. This is not a 2 stroke that uses oil from the gas to lubricate the rotating assembly.

While you are in the carb, there is a 1 way valve in the carb body and the float bowl. CLEAN THEM OUT!


after that, adjust the fuel screw properly. If that does not help, then start playing with the AP circuit. The stock leak jet is really good on the yz450s. Never had any issues with the 450s jetting. Also play with the needle clip position.

If nothing else works, then try modifying the AP circuit a bit.

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