Engine Bogs/dies on quick acceleration

6 replies to this topic
  • MountainMax

Posted May 28, 2006 - 06:27 AM


When i am driving slow, and mash the throttle, my engine just stalls out or bogs untill i back it off and try again a little slower, Im guessing this has something to do with the accelerator pump. I set the timing as per the boyesen cover i put on my 06 450. Anyone have seen this maybe can help me out??

  • clark4131

Posted May 28, 2006 - 11:54 AM


Search for "bog", get a cup of coffee and start reading, lots of info...SC

  • odonnks

Posted May 28, 2006 - 04:49 PM


Sounds like an AP squirt timing issue.
Have temps changed since when it did not do this?
Have you previously done the the AP linkage adjustment per the manual.
Are you still at the stock leak jet of #50?

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  • Numskull

Posted May 28, 2006 - 04:52 PM


Do you guys still do the bk mod on the newer bikes?

I would probably do it because if I twist my throttle all the way back instantly, it will bog. But if I pull it just slightly slower than instant, I will go really fast real quick. :D

I'm not gonna do the mod, as it seems easily compensated with rpms and clutch feather. Just dont try going from 1200 rpms to 11000 instantly without a clutch flick and you will forget that your accelerator pumps just allittle to much on the low side :applause:

  • MountainMax

Posted May 28, 2006 - 05:24 PM


Im jetted as the stick thread above, with 48 pilot jet, I adjusted the pump as per the manual and used the boyeseen tool to set the gap ( it was off a little ) still feels like a big lean bog.... Maybe I will have to adjust the pump timing to squirt a little quicker. I done a search on 'Bog' and whoa, lots of info there, will keep searching those threads.

  • Stiletto_72

Posted May 30, 2006 - 08:12 PM


I jetting matts 05 wr450f with the boyeson cover and moose racing jet kit. I had to put a 60 leakjet in his bike to get rid of the off idle bog. I also adjusted the accelerator pump timing by putting a 3mm allen wrench under the throttle valve and adjusted the accelerator pump til there was zero free play. His gap using a set of digital callipers ending up being .103 inches. Boyesen recommends .100 inches. Adjust for zero free play and try a larger leak jet.

I just posted in the jetting database section the altitude, jets, etc.. used.

  • Thumper_Bloke

Posted May 30, 2006 - 08:34 PM


Did anyone notice there are different pump diaphrams available with different rivet heights? I just bought my 2004 a few weeks ago and have been troubleshooting the Accelerator Pump. The AP wasnt working at all when i started checking it. I took the carb off, and could use my finger to get a "Pump Shot" squirting, but the linkage was NOT doing a thing. So i made the AP arm spring tighter, put in a 40 leak jet, took 1 mm off the rivot and now i finally get a shot of gas, but its still not enough at the start of the throttle opening. So, I am thinking the diaphragm is actually dried out. The bike sat a long time and the float was stuck with varnish. I am going to get a new diaphram and try that. The engine response is so much better, but its not perfect. More to come....


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