Rhythmic fuel leak when in garage

[Anonymous]

Howdy, folks. I've read all the posts on here regarding fuel leaks, and I suspect I have a bad petcock, or need to clean my carbs, or both, but it's doing something weird that I haven't seen mentioned.

First, some info:

1978 GS1000
almost 60,000 miles
oil changed about 1000 miles ago
been running great for me for about 3000 miles

About a month ago, there was a small pool of fuel on my garage floor one morning (I commute to work daily on this bike). I made a mental note and went on my way.

This evening, about an hour after I had arrived home from work, the fuel puddle was back. I took a closer look and saw that the drain hose coming off the far left carb (number one? it's on the far left as I'm sitting on the bike, closest to the petcock.)

Here's the odd part. The hose is spitting out about an ounce of fuel, every two or three minutes. The bike currently hasn't run in about five hours, but I've observed the fuel leaking out for the past hour or so. My gas can is filling up.

I haven't done any major maintenance on the bike as of yet (only had it a few months, and this is the first major incident), so I haven't seen the carbs from the inside. My first inclination is to take the babcock out and have a look, and replace it if need be. Hopefully there would be something obvious in there. Second, spend the weekend, plus the next weekend, and probably the weekend after that, cleaning the carbs, putting them back on, taking them out again, etc., while figuring out another way to get to work.

It's just that the 'rhythmic' leak has me confused. The only thing I can think of is that maybe the combination of a blocked line/bad diaphram/??? is giving me a 'capaciter effect', in that a small leak is building up, filling space somewhere, and every few minutes the dam bursts, spills the fuel, then starts all over again.

Has anyoe seen this happen? Any other ideas than what I already have? Will this thing stop leaking tonight?

Thanks a lot, folks. I've read a lot of valuable information in these forums, and I'm hoping that someday I can contribute some, too.


-Matt

[arveejay]

I have one carb which use to leak a little and I found it to need new needles and seats. While I had ordered them and was waiting for them to arrive I couldn't stand the thought of not riding for 2 weeks. I went to the local TSC and bought an inline fuel shut off valve to close when bike was sitting. This is not a long term fix. Monitor your crankcase oil for a rising level or gas smell. Oil diluted with gas does not lubricate.

[Anonymous]

Your petcock must be leaking along with a float valve probably. Pull your gas line into the carbs off and watch it. The only time it should flow fuel is in the prime position. In Run and Reserve, it needs a vacuum applied to the diaphragm inside to allow fuel to flow. A pair of vise-grips will stop the fuel flow while you wait for a rebuild kit for the petcock(if it indeed needs it) or the float valve and seat. Bob

[Anonymous]

The fuel is getting in there because of a combination of a carby float valve not working (check them all) and the petcock not turning off when it should, thus allowing the bad valve to keep draining the tank. The petcock probably has a bad diaphragm.

I'm guessing that the rhythm comes from the carb overflowing, filling the top level of the air box until the fuel high-tides the drain tube and starts to drain out, but the surface tension of the fuel, once broken, doesn't stop the flow until the level is just below the drain tube level. Then the fuel level builds up again. The cycle will probably be different with the bike on centre stand/side stand.

Kim