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usmc_brianw

04 yz450f dies during acceleration

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Today my 04 yz450f died multiple times doing exactly the same thing. Rode trails, hill climbs, technical, and some faster sections, no problems, runs great. Get down to the main dirt road open it up, cruising in 4th dies after about 3-5 minutes, every time. The bike accelerates fine otherwise, no hesitation, does everything I ask of it. When it dies it's like hitting the kill switch. Won't restart for about 5 minutes, at all. I read some other threads about similar issues. Ideas where to start? electrical, fuel issue, carb issue, vapor lock? Thanks in advance for any help.

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Inspect the gas cap. Remove it and separate the vent hose from the in-line check valve. With just a hose connected to the cap, you should be able to blow air into the vent fitting and through the cap fairly easily, and find it more difficult to draw air through from the cap in the reverse direction. Test the check valve in the same manner. You'll find an arrow embossed on the valve, and air should flow in the direction it points. Be sure it point to the cap when you put it back together.

If it quits again, try unscrewing the cap and listen for a rush of air into the tank. If you hear that, and loosening the cap makes it able to restart immediately, you have a vent problem.

If it doesn't "fix it", you may have a clogged filter screen on the petcock.

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Inspect the gas cap. Remove it and separate the vent hose from the in-line check valve. With just a hose connected to the cap, you should be able to blow air into the vent fitting and through the cap fairly easily, and find it more difficult to draw air through from the cap in the reverse direction. Test the check valve in the same manner. You'll find an arrow embossed on the valve, and air should flow in the direction it points. Be sure it point to the cap when you put it back together.

If it quits again, try unscrewing the cap and listen for a rush of air into the tank. If you hear that, and loosening the cap makes it able to restart immediately, you have a vent problem.

If it doesn't "fix it", you may have a clogged filter screen on the petcock.

The check valve was the culprit, what a relief! Thank you much for the reply.

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