Petcock leak - gas in vacuum tube --> damage?

[Anonymous]

Hey,

I've just noticed a problem with my petcock (the weird one with just a screwdriver slot from the 1980 GS550L). I just cleaned out the carbs due to a decrease in gas mileage over the past few months as well as a possible gas leak that I couldn't locate. I was about to sync the carbs and had the gas tank on a long gas tube so I could work on the carbs. Since my prime doesn't seem to work, I usually attach another tube to the vacuum port on the petcock and gently suck on it every now and then to allow gas to flow.

This time, I was just refilling the carbs with gas initially by sucking on the vacuum tube gently, when I noticed that gas was starting to come into the vacuum tube (and a decent amount at that). Luckily, I was watching and the tube was clear, or else I might have turned into a fire breathing dragon (or at least gas drinking one). I carefully repeated this a couple times and allowed the gas to drain, and each time it fills rather rapidly with gas.

So, my assumption is that I have a hole in the diaphram in the petcock that is going to need fixing. But my bigger concern is whether gas going through the vacuum port on the carbs could have damaged anything, especially if it's been going on for a few months. The #1 and #2 cylinders haven't been firing well recently either, which I assume could be related if that gas leak would cause them to run rich.

Thanks!
--Tyler

[fgh]

There is probably not much damage except to the rubber flanged tubes that go between the carb and cylinders. These might be damaged by excess amounts of gas but my guess is that they are probably OK. If there was enough gas to damage them during the past two months I think the bike would have been flooding so bad that it would have been running very poorly. On my 83 GS750ES the primer line connects to the number three carb. You might have significant carbon build-up in the intake manifold(s) and cylinder(s) the primer vacuum is connected to. If it were mine I'd get the petcock fixed or block it off and not worry about it unless the bike wasn't running right.

[mach]

If you smell gas in the crankcase, you may want to change your oil after rebuilding the petcock. The gas can leak into the cylinder, past the rings and into the crankcase. This is more likely in a bike that sits more than it is used. Long term, the gas can also ruin your clutch plates.
Just something to be mindful of......

[SqDancerLynn1]

I would replace the petcock, get one that has a reserve

Pingle or OEM style towards the bottom of the page

http://www.cyclewareables.com/pages/street_motorcycle_petcock_oem_and_custom_units/fuelpetcock.htm