WR400 stalls if you so much as think about toughing throttle

12 replies to this topic
  • DannyChaos

Posted May 22, 2014 - 10:25 AM


Picked this bike up over the winter and started stockpiling parts for a little spring mini build.

Installed the Hotcams autodecomp exhaust cam and did a full valve adjustment while I was in there.With everything back in spec I rolled the motor over a few times to make sure I was in the clear and put her back together.

Now the bike fires up first kick,no choke and holds a normal idle. Its when you try to give it any gas at all that is stalls out.

I'm wondering if I may be a tooth off on that exhaust cam.

Any info would a and I thank you guys in advance.


Edited by DannyChaos, May 22, 2014 - 10:26 AM.

  • Krannie McKranface

Posted May 22, 2014 - 10:52 AM


It sounds like the mainjet or needle clip fell out

  • DannyChaos

Posted May 22, 2014 - 12:05 PM


Anything's possible. Haven't been in the carb yet on this bike,guess that's next.

Thanks for the advice

  • ncampion

Posted May 24, 2014 - 01:37 PM


Also check the acc. pump in the carb.

  • Rctaz

Posted May 27, 2014 - 05:38 AM


start with the acc. pump before you do anything else to it.  that's more than likely the culprit!!

  • Krannie McKranface

Posted May 29, 2014 - 05:21 AM


The apump does not have affect unless the throttle is turning fast.

Slow throttle won't even activate the apump

The bike will start and run without a main jet or needle, until you turn the throttle

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  • grayracer513

Posted May 29, 2014 - 10:56 AM


More probably, the main jet is plugged, or there's water bobbing around in the bottom of the bowl.  Water will not pass through a jet, and may not be deep enough to get to the pilot.   The jet needle dropping into the jet because of a disengaged clip will do the same thing. 

  • MANIAC998

Posted May 31, 2014 - 03:53 AM


Like KoolAid and grayracer said. Either scenario will prevent the bike from running when opening the throttle. One tooth off on the cam timing shouldn't have enough effect to prevent the throttle from being opened. It might cause other issues, but not that one.

  • DannyChaos

Posted June 02, 2014 - 02:37 AM


Thanks for the quick responses guys. Life came up and prevented me from being able to wrench on her. Some free time this week, so I will go through the carb real good and make sure everything is as it should be. I did pull it and popped the bowl off figuring I would find some sludge or dirt. To my surprise it was spotless? I'll keep you guys posted and again, Thank you

  • Krannie McKranface

Posted June 02, 2014 - 05:00 AM


 The bowl area is only 30% of the carb...........

  • grayracer513

Posted June 02, 2014 - 09:22 AM


Next then, remove the main jet and have a look at the metering orifice.

  • DannyChaos

Posted June 04, 2014 - 04:14 AM


I'm aware. Just didn't have time to get into it.

  • DannyChaos

Posted June 05, 2014 - 10:01 AM


Alright. Carb cleaned and it definitely helped. Starts very easy, holds a pretty normal idle. Now it has the notorious off idle bog and hangs up in the rpms a bit. This is currently 1 of 6 bikes I own, the only one with a single carb besides my xr50 and the only one I'm having problems with lol.


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