Carb flooding?

[Guest]

i have read on here that what ever you do don't leave the petcock in the prime position. If done so so it will fill the motor full of gas. Today i drained the oil out of my gs1000 and i bet half of it was gas. I am wondering what causes that if the petcock is left on prime. Any other carbs i have ever messed with never did such a thing. don't the floats shut off the gas flow to the carbs when the bowls are full. If the floats shut off the fuel then how is it getting in the motor? Am i missing some thing?

Thanks,
Daniel

[chuck hahn]

The oring on the plunger that seats against the front halfof the petcock body gets hard and starts to leak. The diaphrams also seep. So, even with proper working floats fuel can back up and flow down the suction hose from the petcock..thru the carb..then into the cylinder. From there it just passes the rings and fills the oil sump.

Its not a float failure..its a petcock failure. Leaving it on prime never stops the fuel pressure from the weight of the fuel above in the tank..which presses and presses and forces fuel past the internals of the petcock. Follow me???

[Goesman]

Thank you, that makes very good sense. for some reason i was thinking it must be in the carbs. I will rebuild my petcock.

[chuck hahn]

Buy a new one...petcock rebuild kits have about a 25% success rate..if that. And before you buy a new one test it. Take 2 soda bottles and two lengths of vacuum line and run it from one nipple to 1 bottle and the second nipple to the second bottle. Fill the tank and let it sit overnight in the ON ( run ) position. see what bottle..if any.. has fuel in it in the morning. If its coming from the big fuel line nipple or the small vacuum nipple youve got a bad petcock.. If there is no fuel in either bottle the petcock is fine..which then leads to the carbs. Do some testing before you doanything.

[chuck hahn]

problem with CV carbs is there isnt a bowl overflow like on the VM style, so if the floats are leaking the fuel will rise till it runs down the throats and fil the cylinders..and then fill the oil sump. So in theory if the petcocks nipples dont leak in the test the floats could be the culprit. Leaky float needles, bad float seats, floats hanging up on the gaskets at the sides, float seat orings, or improper float hts are the usual things to check in the bowls.

[Steve]

Yes, the floats should stop the flow, in the event of petcock "leakage". However, even if the floats do actually stop the flow, there is still the o-ring around the float valve that is a good candidate for being a leakage source, too.

So, ... if you have fuel in the oil, you actually have TWO "failures", not just one. The problem is that you can have just one failure and not know it, so there is no real warning until you have both of them.

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