77 gs750 carb problem

[budweiser792]

i pulled my tank and noticed that my petcock wouldn't shut off so I figured that i might need one of those. Does anyone have someone that has one or know where I can get one for a decent price. Well I pulled the left bowl off my bike to see how they looked and they looked great, so when I put it back on and put the tank on it now will fill up and leak from the port or vent on the bottom of the first carb only. Just wondering if its the petcock that needs to be replaced or something in the carb that I might have missed. I got the bike for free and don't really don't want to sink a bunch of money into it. But if it needs it I will get it the parts to fix. The bike is in great shape other than that. Thanks

 

[81gs750bagger]

i pulled my tank and noticed that my petcock wouldn't shut off so I figured that i might need one of those. Does anyone have someone that has one or know where I can get one for a decent price. Well I pulled the left bowl off my bike to see how they looked and they looked great, so when I put it back on and put the tank on it now will fill up and leak from the port or vent on the bottom of the first carb only. Just wondering if its the petcock that needs to be replaced or something in the carb that I might have missed. I got the bike for free and don't really don't want to sink a bunch of money into it. But if it needs it I will get it the parts to fix. The bike is in great shape other than that. Thanks

bike bandit or z1 enterprises and sometimes you can find a nos one on ebay

 

[Nessism]

If leaks fuel out of the overflow tube you have a problem with the float needle on that carb. The petcock will help keep you from dumping a full tank of fuel on the ground, or into your crankcase, but the primary issue is the float.

 

[jonr]

Budweiser,

It may be the float itself. I had a problem with #3 (same VM carbs) many years back where the float was rubbing up against the float bowl housing and getting stuck, in effect leaving the float needle open. I just gently bent it over about a half a millimeter to give it the needed clearance.

This would be my guess since you only took off the cover and probably did not have an opportunity to get any gunk into the float needle valve while it was upside down.

J

 

[twerth]

Hey Budweiser,
I was wondering if you ever got your problem fixed. I have a 78 GS750 that's doing exactly the same thing. I can't park it in the garage over night because it will stink the whole house up.

In an effort to trouble shoot, I swapped the needle valves in #1 and #4, but #1 still leaks. The next chance I get to take the carbs off, I'll check for interference like jonr suggested. Another sanity check might be to put the problem float and one from a good carb in a can of gas and see if they both float at the same level. I've heard these things can soak up over time and not float like they should.