WR 450 getting on my nerves

I've got a 2005 WR 450. It does not want to keep running. This thing will fire up on the first kick. It runs great, good power, but after 4 or 5 laps around the house it dies. It sounds like it is being starved of gas. I have a JD jet kit on it and just shimmed valves yesterday. I pulled the carb and cleaned it and the float and float valve is fine.

After the bike dies it does not want to start.

Any ideas would be appreciated before I throw this thing to the curb.



Yo buff,

Check your gas cap and the check valve in the vent line to make sure it is breathing properly. If it is not, it will create a vacuum in the tank as gas is consumed, prohibiting the flow of fuel to the carb. Ride around with the cap loose and see if that cures the problem.

Let us know how it goes.

Thanks MJ,

I've checked that as well. In fact, whover had the bike last put a cap on that's the wrong size, it leaks.

I have taken the cap off and tried to restart. No success.

Starting to think of accelerator pump issues.


It's not the accelerator pump, that only comes into effect when opening the throttle quickly and squirts extra gas in for better response - it has nothing to do with the engine stalling out.

Carb vent hoses? Check none of them are blocked.

Empty the tank into a clear container, check for anything in it, take off the gas line from the tank to the carb, check it.

Check the flow of gas from the tank, you may have something inside that gets sucked into the opening.

If it were me, After cleaning the gas tank and checking that system, I would put a YZ450 needle in it and start from there. Clean out the carb in the process checking the floats, pilot, main jets, etc. Then clean the air cleaner and make sure your getting the right fuel and air mixture. Then look at the top end starting with the plug. That's me.

Thanks guys,

I should also add that the machine dies when I am just starting to crack the throttle.


Thanks guys,

I should also add that the machine dies when I am just starting to crack the throttle.


Look at your leak jet and AP timing:excuseme:

Are you sure you did the shims right? I've a mate with a 08, that was going good until the shop did the shims. Now, as soon as it's warmed up, it's a pain to keep running, and stalls, at every chance that it get's. Just a thought.

OK Guys,

Went to the bike this morning and it started right up. Did about 5 laps around the house and then the bike quit. I pulled the plug it looked good and dry. Kicked the bike with the plug out and have good spark.

I pulled the ignition coil off the bike and put a multimeter on it to run the tests in the manual.

Primary was 3 ohms and secondary was an open circuit. Both failed the specs in the manual.

Just wondering if anyone has had the same problem.


heat causes a coil to fail, so maby its on its last legs

keep in mind i got 20k miles on mine and still going strong..

o the die on acceleration is normal..you are at too low of an rpm range the pump squirts too much fuel and dies. you must learn to roll on the throttle

I've heard of bike with similar problem as yours and it was in fact the ingition and not the carb. As the bike warms up so does the ignition coil. As soon as the ignition coil warms up it goes haywire.

Just put in the new coil today. I've only run the bike around the house but the thing runs the best it has ever run.

Hope this might help someone in the future.


Hope this was the fix. If sucks if you cant trust your bike to finish a long ride.

Been there and done that with a 98 YZ250 and bad cdi box. Good luck.

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