BACKFIRES



5 replies to this topic
  • gal

Posted February 27, 2002 - 10:05 PM

#1

MY BIKE STARTED TO BACKFIRE A LITTLE, ONLY WHEN I TAKE MY ARM OFF THE TROTTLE AND ONLY A LITTLE, BUT IT NEVER HAPPENED BEFORE. ITS A 2000 YZ426 WITH AROUND 4000-5000 KM . WHAT CAN B THE CAUSE? CAN IT B VALVE CLEARENCE? NEVER CHECKED IT BEFORE....

  • FOX426

Posted February 27, 2002 - 10:50 PM

#2

Do you have stock jetting? If so and the temp drops below 50-F it will pop on deceleration (common). Valves out of spec can cause several proplems, is it getting harder to start? If you have more than 100 hours on bike it is definitley time to check valve clearance. Good luck. :)

  • aag800

Posted February 27, 2002 - 04:13 PM

#3

Try turning the fuel screw out 1/2 a turn at a time and test it out. If you have to go 3 or more turns out from fully seated to get it to stop popping, go to a richer pilot jet. -Adam-

[ February 27, 2002: Message edited by: akg800 ]

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  • aag800

Posted February 27, 2002 - 04:15 PM

#4

Try turning the fuel screw out 1/2 a turn at a time and test it out. If you have to go 3 or more turns out from fully seated to get it to stop popping, go to a richer pilot jet. You should also take the carb apart and make sure none of the jets(air or fuel) or fuel passages are clogged. And clean out the Acc. pump diaphram while your at it. Later -Adam-

  • aag800

Posted February 27, 2002 - 04:18 PM

#5

I don't know what happened with the double post. Whatever!

  • Shawn_Mc

Posted February 28, 2002 - 08:14 AM

#6

Is it spitting back through the carb or popping out the pipe? Carb is lean condition or tite valve. Pipe can be a couple of things, leak at header to head most common. All things being equal Id check the header to head connection. Pop the header off and look for a dark spont on the sealing face of the header pipe. If youve got a dark spot youve found your leak, hence your pop! I really shouldnt be a jetting thing, unless something else caused the mix to be wrong (Ie piece of dirt etc)





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