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klxer's HELP!

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I posted in the jetting forum but got no replies??? anyway my situation is I have a random popping/backfire at idle. Ive had the carb off a couple of times now just to make sure I didnt miss any passage ways. I have a klx 300 with a 330 kit. I sold the original carb and bought a used mikuni 36 PUMPER It starts great. It will idle as high or low as I want it to but its got this random popping out of the exhaust. Pop, idle, idle, pop, pop, pop, idle, pop, idle. Ive adjusted mixture screw both ways and it seems like its doing what its suppose to but the popping wont go away. If at idle I stab the throttle it will hesitate for half a second or so then it catches itself and rev smoothly. When it does catch itself it pumps out alot of black smoke. I havent had time to dig into anymore. Im assuming the hesitation/catching itself and black smoke may be pump adjustment. Ive searched endlessly for popping/backfire on the forums but they are all popping on decel. HELP!!!!

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Black smoke means too much fuel. Sounds like the pump is squirting to much at throttle up. A popping or backfire is fuel that is not being burnt during combustion. raw fuel is igniting in the exhaust system. What size Idle and main jet are you running? Go Green :thumbsup:

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If at idle I stab the throttle it will hesitate for half a second or so then it catches itself and rev smoothly. When it does catch itself it pumps out alot of black smoke. I havent had time to dig into anymore. Im assuming the hesitation/catching itself and black smoke may be pump adjustment. Ive searched endlessly for popping/backfire on the forums but they are all popping on decel. HELP!!!!

I have a suggestion for this part of your problem. Yes, you may need to adjust when the pumping starts and how long it squirts. Both of these adjustments are on the carb. I set the "squirt start" to coincide with a small opening of the throttle. "Squirt length" was done by cracking the throttle and doing that adjustment for best throttle response . Most likely your accellerator pump is pumping too much gas. You'll need a small allen wrench to do the adjustments.

Ride on

Brewster

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