Float Bowl Still Leaking

[rickt]

Installed the replacement needle and seat from K&L into carb #1 of the '78 GS750C. Pulled all the float bowls and checked the float heights. Everything looked good. Installed the carb rack and the airbox, hooked up the auxillary gas tank and she started right up. gas again leaking from the #1 float bowl vent tube. Doesn't seem to leak when the bike is running - when I blip the throttle, gas spurts from the hose.

Don't know where to go from here. I still have the original needle and seat and I suppose I could clean the parts and reinstall. Tried rapping on the bowl just in case the float was hung up. This did not solve the problem.

Learning how to remove and reinstall the carbs and airbox - not an activity that I care to repeat multiple times. Any suggestions on how to resolve this problem short of replacing the carb?

rickt

[ryonker]

Hi Rick;

I am from White Bear Lake. You should come on our GS ride in July.

How high up is your aux gas tank?

Rick

[Toadlips]

Hi Rick,

Your situation sounds a little different than mine, but I thought I'd throw my 2 cents in. My #1 carb was leaking very slightly on my 77 GS750, and I tried all the usual tricks, too (valve & seat, float height). It ended up being a VERY slight hairline crack running up the float bowl tube. It was not easily visible to the naked eye. The way I discovered it was by taking off the bowl and filling it with gas. Sure enough, it started dripping! I ended up replacing the bowl, which fixed the problem!

Now, you're saying that the gas only comes out the overflow when you blip the throttle? Is it possible that you're backfiring through the carb and forcing the gas out of the overflow? I've never personally seen that, but aside from the above items mentioned, I can't think of anything else.

I'm sure one of the gurus on this site might have some more insight!

Good luck!!
Toadlips

[tkent02]

You have your float bowl vents plugged?

[rickt]

Ready to investigate other causes

ryonker,

Good to see another GS'r close by in White Bear. I would like nothing better than to participate in the July GS ride. But, first things first - I need to get this bike running the way it should without having to carry a fire extinguisher with me.

I hung the auxillary tank from the mirror stem, so it is about handlebar high.

Toadlips,

Yes, I'm beginning to think that the problem might have something to do with the float bowl. I have an old crappy set of carbs. I think I'll pull a bowl off, clean it up and try it on leaky #1. Yes, there is some weak backfiring through the carbs before the engine warms up, but the gas leaks out even after the engine is shut down.

tkent02,

Exactly where is the float bowl vent and how do I check the vent for a plug?

Thanks for the suggestions!

[blizzard]

Hi Rick,

Your situation sounds a little different than mine, but I thought I'd throw my 2 cents in. My #1 carb was leaking very slightly on my 77 GS750, and I tried all the usual tricks, too (valve & seat, float height). It ended up being a VERY slight hairline crack running up the float bowl tube. It was not easily visible to the naked eye. The way I discovered it was by taking off the bowl and filling it with gas. Sure enough, it started dripping! I ended up replacing the bowl, which fixed the problem!

Now, you're saying that the gas only comes out the overflow when you blip the throttle? Is it possible that you're backfiring through the carb and forcing the gas out of the overflow? I've never personally seen that, but aside from the above items mentioned, I can't think of anything else.

I'm sure one of the gurus on this site might have some more insight!

Good luck!!
Toadlips

I found the same crack on one of mine this year and it had an annoying leak .

[rickt]

Update - Float Bowl Vent Leak

Pulled a bowl off the spare rack of carbs, gave it an overnight soak, and installed it last night. Bike fired right up and after several minutes I could detect no gas coming from the vent of the problematic #1 carb. So, it would seem that the float bowl was the problem player. The true test will come with more run time.

Now, I just have to repaint the tank. Due to my lack of attention this beautiful painted piece took a tumble and bounced a couple of times on my garage floor. I guess these events help justify the money I spent on spray guns and a hefty compressor.

rickt