Bike Wont Idle right when I'm taking it out of town!

So I started my bike today to warm it up and change the oil and it wont run without the choke on. When I turn the choke off it dies right away. If I give it a little throttle then turn off the choke it backfires like crazy spitting blue flames out the pipe. This is an 04 WR450 with free mods done, a YZ silencer and JD jet kit. What I believe is going on is that the valves have gotten so tight that it is causing this condition as I have never adjusted the valves and don't have the feeler gauges to check them. Would tight valves cause this condition? Just wanted to get this out there I'm off to check the color of the plug. Any help would be appreciated as I am supposed to be loading my bike in the trailer right now to be going on a 4 day trip to the mountains on Tuesday after work. Oh and I know I'm going to get bashed for not checking my valves but I ran my 2000 WR400 for 4 years and never checked the valves on it ether and it ran fine until the day I sold it, not saying that its the right thing to do but any way let me know what you think.


Clogged pilot jet. Replace it.

I guess if the valves are the issue then it wouldn't run at all, whether you pull the choke or not.

Can you be more specific on whether the bike didn't run for a while ? Does it shut down when you open the throttle with the choke pulled out ?

I had a different bike a fe weeks ago with a similar problem. In this case, the bike had not run for a prolonged period, and the fuel had dried out in in the carburator. When it does, it leaves a sticky gum that can block the jets in the carburator.

Because the choke uses another circuit your bike still gets fuel when it's pulled, but as soon as you close it, no more fuel goes to the engine.

If this is the case you need to clean out the carburator and jets.

Just my toughts. Don't shoot me if this is not the cause. It's difficult to assess based on text :busted:

Installed a new plug, still the same issue. It will run at high RPM's but when I back off the throttle closer to idle it will start to back fire and when I let off the the throttle it just dies. It acts the same with or without the air filter installed, I have it out right now.

I agree with the previous posters. If your bike has sat for a while than your pilot jet is probably plugged (fuel will varnish and plug that small opening). Clean the pilot jet and ride.

I'll give it a shot.


Cleaned the jets and she purrs like a kitten. Must be my own guilt about not checking the valves making me think that was the problem.

Thanks for the feedback. I'll be loading up the trailer tonight heading to the smoky mountains tomorrow after work. :busted:

The pilot jet can be a finicky gremlin to a bike that sits for awhile.

If the bike is going to sit for any length of time (week or more) turn off the fuel and drain the float bowl entirely. You'll never have this issue again if you keep it empty while stored.

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