Help! WR 450 trouble

7 replies to this topic
  • WR450F pilot

Posted August 03, 2008 - 02:42 PM


Hello everyone!

Let me begin by saying after reading many posts on here that it's obvious that there is an extensive knowledge base availible!

Now, with that being said I need some help and would like to tap into that knowledge. I have an 07 WR 450F that I can't get enough of, but have starting havin issues with it.

Had fired it up and was riding normal (no hard-core stuff) on the track and about five minutes into it the bike started to backfiring, popping, mis-firing, and then died. The whole episode lasted a few seconds at the most. It absolutley would not start again so I let it sit for about 10 minutes and it fired right up only to repeat the same thing within a few minutes.

Know I'm an old school MX'er from way back when and have had many bikes in the past, but with the technology of todays bikes I do believe this issue is over my head.

I did take the spark plug out and it was fine (visually). I have since started it in the garage and again, within a minute it does the same thing. Have also cleaned the air filter and pulled the fuel hose off to verify fuel flow. To date that is all I've done.

Any ideas? It's killing me to have one of the meanist bikes around, but not able to ride it! Not to mention the kids having to wait on me!;) :ride:


Posted August 03, 2008 - 03:54 PM


Could be a bad coil. This is the way they usually fail.

  • WR450F pilot

Posted August 03, 2008 - 05:26 PM


I was thinking the same thing, but when I spin it over with the plug out I see a very good blue spark. Any chance it would prove good cold and then fail when hot?

  • tweav

Posted August 03, 2008 - 07:29 PM


I think I would try the dirt in carb thing first . I've had the same sort of thing happen to my o7 and it was dirt floating in the bowl . pop the bowl off and clean it and the jets too while your there.

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  • Alternative

Posted August 04, 2008 - 12:44 AM


First off try a new spark plug, even if the one you're using "looks" fine, it may not be and may be failing once it's warmed up. If that doesn't help and your carb is clean then your diagnosis of a buggered coil is probably correct.

  • Strattos

Posted August 04, 2008 - 01:59 PM


Could also pay to check your spark plug lead. I had similar problems, although not as severe. Traced it to a faulty resister in the plug cap.

  • WR450F pilot

Posted August 04, 2008 - 06:23 PM


Well, looks like I'll be spending some time in the garage tomorrow! Everyone seems to be running scared from this tropical storm coming in so I ended up getting the day off. At any rate, I'm glad to know I'm not the only one who has had some type of issue. Thanks for all of the advise so far. I will purchase a new plug and try that first. How do you go about checking your plug lead? I guess the next thing would be check the carb. Anyone have any other suggestions? I'm all ears at this point!

  • jbrooks26

Posted August 04, 2008 - 06:28 PM


Could also be some water in the fuel, causes very similar problems. When you pull the float boal plug out, don't tip it upside down and look for water in the bottom of it. If there is any water there, drain fuel into a container until no more water is coming out of the petcock. Make sure you do this with the valve on RES or you will leave a good amount of water in the tank if that is the problem. Hope this helps.



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