I have a 2006 yfz 450 it has an X-6 sparks exhaust k&N air filter Sparks/Dynatek CDI, and cam mod. The bike runs awesome but it backfires on deceleration. it has always done this but now that i have added the cdi it is more pronounced. I have been told to open the air fuel mixture screw a 1/4 to a 1/2 turn and it should be fine does anyone have any idea where that screw is on this bike? Maybe under the carb? Or perhaps any other solutions to the backfiring? Before the CDI addition it really ran great no issues other than some crackling and popping.

Any help would be great.

bottom of the carb. You'll have to remove the carb or somehow turn it on its side.

Consider one of these to make your life easier, makes adjustments much more practical.
http://www.ziptyracing.com/products/produc...spx?id=MTEwMQ==


Backfiring is normal. If the screw adjustment doesn't help, try a slightly larger pilot jet.

Thanks i will try that.
and buy the part you recommended.

keep messing with the pilot screw. If you have to go over 2 1/2 turn, then bump the pilot up and start at about 1 1/2 out.

what he said. i have an 05 and run it at about 1 1/2 out. go on ebay and get that screw. you mide have to drill a hole in the carb since some came caped of. when changing over to the screw be very carefull since there is a very small o-ring,washer, and spring in there and can easly be lost.

The popping on decel is a classic symtom of a lean pilot circuit. You will most likely need a larger pilot jet.

Popping on decel is caused by two things, A lean condition or a air leak. Make sure you tighten your exhaust. I would start with a 170 main and 45 pilot with the fuel screw out 2.5 turns. Good luck.

What jetting are you currently at?

But yes, it sounds like the pilot is too small. If your screw is not affecting anything, your pilot is not correct.

Bump up your pilot jet......

Be careful running the zip tie. They will fall out easier than the stock screw.

I have something on my 05 for that has a little o-ring on it that keeps it from spinning out. I bet you could put one on the zip-ty to make it stay. I can't figure out what I bought and i'm sure as hell not removing it to look.