wr 450 hisitation and backfire


5 replies to this topic
  • visioncarpentry

Posted October 02, 2011 - 07:40 AM

#1

Yamaha fans, MY WR 450F NEEDS HELP!

i have a 2004 wr 450f and it has developed a bad hesitation. i took out the carb and cleaned it and put it back in and then it developed a backfiring problem. i thought i must have blocked a jet up with dirt when i was cleaning it so i took it apart again... Three more times i did this with no results. so i took it to my mechanic who also took apart the carb and changed the plug, again no change... i now believe this problem to be electrical because with throttle on it pulls and pulls with no hesitation and when it does hesitate its almost as if i turned the key off and right back on for a split second. The hesitation is only at constant rpm and it worsens as it gets hotter and it backfires when i down shift.

GUYS ANY HELP??? TPS, COIL??? even my mechanic is stumped and the more stumped the more i get charged $100.00/hr for him to think...

  • xxxshiftxxx

Posted October 02, 2011 - 05:37 PM

#2

Start trouble shooting a electrical problem if u think that might be the problem. Disconnect the TPS and see if it fixes it. If it does, then set the tps with a multi meter and the manual, or buy a new one. Borrow a cdi from someone, and see if that fixes it.


Make sure u put the carb back together right and set the fuel screw right.

  • The Hill Boys

Posted October 02, 2011 - 06:51 PM

#3

I went round and round with backfire issues. Here was the result...

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  • xxxshiftxxx

Posted October 02, 2011 - 09:14 PM

#4

Good point. Make sure u put that bad boy on right, the hole down. And check the oring on it.... Wont run right if its up side down...

  • tomk

Posted October 03, 2011 - 06:50 PM

#5

could a bad seal be the prob on my bike, if I accelerate hard in any gear then let off and let the engine slow the bike down it pops quite a bit, not hard or super loud but it does it quite a bit? I was thinking it was that the valves needed to be shimmed but the clearance checked out :smashpc:

  • dgcars

Posted October 04, 2011 - 01:43 AM

#6

Yamaha fans, MY WR 450F NEEDS HELP!

i have a 2004 wr 450f and it has developed a bad hesitation. i took out the carb and cleaned it and put it back in and then it developed a backfiring problem. i thought i must have blocked a jet up with dirt when i was cleaning it so i took it apart again... Three more times i did this with no results. so i took it to my mechanic who also took apart the carb and changed the plug, again no change... i now believe this problem to be electrical because with throttle on it pulls and pulls with no hesitation and when it does hesitate its almost as if i turned the key off and right back on for a split second. The hesitation is only at constant rpm and it worsens as it gets hotter and it backfires when i down shift.

GUYS ANY HELP??? TPS, COIL??? even my mechanic is stumped and the more stumped the more i get charged $100.00/hr for him to think...


A constant speed hesitation is pretty normal. I've had WR's for a long time and they have all done it. I found that to minimise it as much as possible, the pilot circuit had to be set up perfect and the correct needle installed. Try putting the clip on the top notch and comparing the change with it on the bottom notch. A richer needle in the 1/8 to 1/4 throttle range might be the way to go.




 
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