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Old 19-03-2014, 19:32   #1
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Yamaha Enduro -- Air leak?

Two stroke Yahama 8HP Enduro. We pump the bulb to start the engine. It starts and runs for a while. While underway, the bulb goes "soft" and the engine dies. So, one hand steering and one hand pumping to keep her going.
Am thinking an air leak in the system somewhere?
Anyone with the same problem? Anyone with ideas on common failure points?

THANKS!
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Old 19-03-2014, 20:09   #2
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Re: Yamaha Enduro -- Air leak?

Sounds like you may have a fuel pump problem. The pump has two check valves like any diaphram pump. If one goes bad it stops pumping fuel. When the carb sucks the carb bowl empty the engine dies. The bulb works the same way, with two check valves, with your hand providing the motive force to keep the fuel flowing. It's pretty common for a piece of debris to get caught in a check valve and hold it open. If it can't close when it's supposed to the fuel pump won't work. One common source of debris is the fuel filter. If it hasn't been changed in a long time it could be breaking down and releasing filter materiel into the fuel system. It's usually pretty simple to diassemble the pump and clean debris out of the valves. If it's not debris it's probably a bad valve. They are included in a fuel pump rebuilding kit. I doubt it's an air leak,
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Old 20-03-2014, 09:01   #3
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Re: Yamaha Enduro -- Air leak?

THANKS! Will try working on that. Have had two mechanics working on this thing so far and neither have even suggested that as an issue.
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Old 20-03-2014, 09:12   #4
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Re: Yamaha Enduro -- Air leak?

Quote:
Originally Posted by S/V Serenity View Post
THANKS! Will try working on that. Have had two mechanics working on this thing so far and neither have even suggested that as an issue.
Holy smoke... You rightly are in need of head banging with two mechanics of this caliber...
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Old 20-03-2014, 09:20   #5
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Re: Yamaha Enduro -- Air leak?

My 2 cents the fuel end clips conectors at the bulb fuel line are not Yamaha original,
check if you see bubles or fuel leaking there when you squeze the bulb...
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Old 20-03-2014, 09:24   #6
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Re: Yamaha Enduro -- Air leak?

I assume you've already checked that the air vent on the tank is open and functioning?
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