Bike pops when engine braking


7 replies to this topic
  • crf250r04

Posted August 09, 2013 - 06:24 AM

#1

I have a 2009 yz450f that seems to backfire a lot more then it used to when the bike is engine braking.  I checked the exhaust for any leaks and couldn't find any ( is there a good way to do this).  Also I put a new piolot jet in the bike.  When the bike is in nuetral it very rarly will pop but once the bike is in gear and I let off the throttle and the engine braking kicks in it will start to pop a lot.  It is starting to get pretty annoying.  Any suggestions would be appreciated.



  • grayracer513

Posted August 09, 2013 - 06:41 AM

#2

Be certain that the hot start is closing and see what it's like when you get the pilot screw set correctly.

 

http://www.thumperfa.../jetting.htm#PJ

 

http://www.thumperta...ad.php?t=327405



  • ohiocoalminer

Posted August 09, 2013 - 06:46 AM

#3

Did you install same size pilot ? If so , may want to go up 1 size on pilot.

  • grayracer513

Posted August 09, 2013 - 07:10 AM

#4

Whether or not the pilot needs to be bigger can be determined by following the instructions in the second link I posted.



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  • crf250r04

Posted August 09, 2013 - 08:40 AM

#5

Thanks, I will try the second link that grayracer posted.  Also I replaced the pilot with the same size. 



  • crf250r04

Posted August 09, 2013 - 08:41 AM

#6

Also what is a good way to check if the Hot start is closing all the way, I know if I pull it in the bike will idle higher, but is there any other way?



  • grayracer513

Posted August 09, 2013 - 09:08 AM

#7

Other than taking it apart and checking for free movement, and ensuring that it has free play at all times as you turn the bars, not that I can think of.



  • McAwesome989

Posted August 13, 2013 - 02:59 PM

#8

i have an 07 450 that backfires / pops when engine braking. last time i had the carb off i had trouble getting the hot start installed properley. when i got it put back together the hot start didnt work. i could pull the lever and it didnt change the idle. it doesnt bother me because my bike starts easy most of the time anyways.besides popping alot it didnt change how it runs. could this be why it is popping / backfiring?







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