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Pulse pump on 2008 300 cc Midwest Roughneck

Go to solution Solved by PKR,

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If the tank is high enough or pressurised enough the fuel could force the valves open and fuel could flow through, but I'd expect the springs holding the valves shut would put quiet a bit of restriction on the flow.. I wouldn't expect it to flow freely.

The valves might seat and work better once it's being used though..  Have you tried it, does it pump ? If it doesn't pump properly, or if it doesn't hold pressure, (only the tiny amount of pressure they work at, about a pound or three per inch), then the valves are defective.

Try holding the fuel hose coming off it up high and see if the fuel in it runs backwards and back into the tank.. It shouldn't of course.

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Thanks for the reply. I don't think it would be pressure from the tank as I just have a small tank attached for testing. I did have the quad running for about 3 minutes before it flooded out. The float is screwed in the carb so I have to wait for a new one before I can run the machine again. I will try seeing if the pump will actually pump or just free flow.

Other than that I'm thinking of sending it back as defective.


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Here's how to test a suzuki pump.. that one is probably much the same..

To test the fuel pump you lay the fuel hose to the carb into a bottle. Lay it on it's side with the hose laying flat. If the hose is dangling down you won't see the fuel pumping out properly. Then suck hard two or three times on the vacuum hose going to the pump, and then let the vacuum off suddenly. You should see a single slug of fuel come out of the fuel hose. The slug should be full diameter of the hose and about ten mills long. If that works then your pump is ok and will work if it's getting good pulsating vacuum.

To test the vacuum you reattach the vacuum hose and start the motor and let it idle. It should pump fuel out of the fuel hose into the bottle at full diameter of the hose and slugs about eight mills long. If that works then the pump is working and it should start and idle at east.

Then you need to check the vacuum is still strong enough when the motor is under load. To check that you leave it all as is but sit on the bike, put the brakes on hard, engage first gear and open the throttle until the motor starts straining against the centrifugal clutch. As the motor starts to labour the pump will likely slow down it's delivery of fuel, but it should keep pumping some. If it stops pumping then you have weak vacuum or a malfunctioning pump.

The vacuum has to be strong, and pulsating, when it gets to the pump. If the vacuum hose has been swapped with some soft thin walled stuff the pulsations can get lost as they suck the vacuum hose flat and then let it out again. Low vacuum can be caused by low compression, tight valves, or air leaks.


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