WR426F backfiring and stalling


4 replies to this topic
  • Endurists

Posted April 23, 2011 - 12:03 PM

#1

Hi!

We got a problem with my fathers WR426F 2001. Hotcams
Bike starts backfiring and stalls at load after disassembling and assembling gearbox.

First idea was timing, checked and tried twice, bike idles good.

2nd idea was valves. Checked all clearances, only one valve had bit smaller gap than necessary. Also checked valves for correct closing, put a petroleum up the valves. There wasn't any leak on valves.

Also checked jetting, the main was 175, and we put back as manual says 165

If technicaly everything is OK, whats next, electrical problem? Do someone had the similar problem?

Edited by Endurists, April 23, 2011 - 12:18 PM.


  • William1

Posted April 23, 2011 - 04:24 PM

#2

Try a new spark plug

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  • Endurists

Posted April 23, 2011 - 11:15 PM

#3

Try a new spark plug


already tried! without changes.

But as I remember, this bike always requires new spark plugs! If father rode few months, then was diificult to start, change spark plug and problem was gone for another few months.

Kalvis

  • Pooley

Posted April 26, 2011 - 07:37 PM

#4

already tried! without changes.

But as I remember, this bike always requires new spark plugs! If father rode few months, then was diificult to start, change spark plug and problem was gone for another few months.

Kalvis


I would disagree with this statement, IF your jetting is decent. I have personally used the same sparkplug for something like 3 years, and the bike started in just a few kicks hot or cold. The only reason I changed it was because the outside was beginning to corrode and I didn't want it to get stuck in the head.

If your jetting is way off, in either direction it will affect the life of the sparkplugs. Does it pop on decel, or only when you whack the throttle? Loud bangs with flames on decel, usually means a lean condition for the fuel screw and/or pilot jet.

If the bike dies when you quickly open the throttle, I would suggest looking at the O-ring mod and also the check the jetting.

Edited by Pooley, April 26, 2011 - 07:58 PM.


  • Endurists

Posted May 01, 2011 - 11:06 PM

#5

I would disagree with this statement, IF your jetting is decent. I have personally used the same sparkplug for something like 3 years, and the bike started in just a few kicks hot or cold. The only reason I changed it was because the outside was beginning to corrode and I didn't want it to get stuck in the head.

If your jetting is way off, in either direction it will affect the life of the sparkplugs. Does it pop on decel, or only when you whack the throttle? Loud bangs with flames on decel, usually means a lean condition for the fuel screw and/or pilot jet.

If the bike dies when you quickly open the throttle, I would suggest looking at the O-ring mod and also the check the jetting.


The problem is with carb. Something is totally wrong there. Even after one kick the spark plug is really wet. Tried to put carb from my EXC525 (also39mm), bike is running perfect with that. What to check? Float level? Float needle? I heard there is some membrane that opens at long downhills and give extra fuel, maybe this part is failed?

Kalvis




 
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