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Mysterious gas leak from carbs

  • Thread starter Thread starter drewaugie
  • Start date Start date
D

drewaugie

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Hey guys, I have a 77 GS750 that I've been fixing up and I'm having troubles figuring out where this gas leak is coming from. It's a very small leak (a couple of drips a day from the carbs) and started happening after I adjusted the needle jet. I reinstalled the carbs, rode it around, and found a little gas hanging from the float bowl drain screws the next morning. I pulled them off and cleaned them and the same thing happened a couple days later. I thought maybe it was coming from the fuel screws or the connectors between the carbs (on which I replaced the o rings from ones I found at the hardware store) so I ordered the o ring set from cycleorings and once again cleaned out the carbs and replaced all of the gaskets and o rings. Same problem but only on the middle 2 carbs. Tonight I took them off the bike and searched for a source. It seemed to be leaking from the top edge of the float bowl as if there were no gaskets. When I took them apart I noticed the gaskets were completely soaked in gas. I'm new to this so I'm not sure if this should be happening but I would assume not. From what I can tell the gas is seeping through the gaskets and leaking out from there. Am I crazy, should I be looking for another source, or get better gaskets? Maybe make my own?
 
Have you checked the fuel level using the clear tube method detailed in the factory Suzuki service manual? If not, you may want to try. The fuel level often creeps up as the spring tips in the float needles gets soft.
 
I haven't tried the clear tube method yet but I'll try that once I get the carbs put back together. I have set the float height as described in the link posted by tom203. I think I'm going to replace the float needles this time to see if that helps. Thanks guys.
 
Check your bowl gaskets also. They can leak and evaporate before you really see anything leaking. If the bike smells a lot like gas all the time it is probably time to change them especially if you leave the bike on the kickstand.
 
So I finally got everything put back together and, of course, it ended up raining for a couple of days. I finally had a chance to go drive around tonight and get everything flowing so I'll check tomorrow and see if I have any leaks.

I realized I was a huge idiot and was setting the floats to the wrong specs. I had set them to 22.4mm but they needed to be at 26mm, so that was most likely the problem. I had read somewhere that some guys will set the floats about 1mm below spec to allow just a bit more gas in the bowl to prevent the carbs from starving when stopping too quick or on a hill. When I stopped quick tonight, I noticed the RPMs drop for just a second, so I'm assuming I'm pretty close to spec now? Also, I couldn't seem to find the drain plugs to connect the clear hoses to on Z1 Enterprises website or anything locally that would work so I haven't been able to check levels that way. Does anyone happen to know what size the threads are so I can find some easier?

BigD_83 said:
Out of curiousity, did you use SGP (Suzuki Genuine Parts) float bowl gaskets, or some aftermarket brand like K&L?
Click to expand...

The last set of gaskets I had were K&L brand and the time before that were from the carb rebuild kit that I got, not sure on brand though. This time I lost patience and got sick of paying $20 every time so I took a stab at making my own. I was pleasantly surprised at how well that went but we'll see how they hold up. The gasket material I got seemed to be the correct thickness and they were advertised to be gas resistant.

I know I should try not to change a bunch of variables at once but I'm pretty confident in the float height now but if anyone can tell me a good place to find SGP gaskets, I might order some and replace the gaskets with those if the leak persists.
 
My gaskets were (before rebuild) and are K&L. I cured my problem by using SS Alan head screws and applying a little more torque. I also stopped parking the bike on the side stand. It resulted in the up hill 3&4 enrichment failing requiring a rebuild. That's the only thing I can figure. The gas smell is gone now and it takes a lot longer for evaporation to affect instant starting. More like a week verses two to three days. I live in an extremely hot and humid climate now so evaporation is a bit of a problem and I don't have a convenient prime on my dreaded "80 petcock on the tank I have.
 
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OldVet66 said:
... I live in an extremely hot and humid climate now so evaporation is a bit of a problem and I don't have a convenient prime on my dreaded "80 petcock on the tank I have.
Click to expand...

That could have been a problem too. Here in NE it's been super hot and humid and my garage is basically a giant humidor. That, mixed with the wrong float height, is probably what did it. Still no leaks after last night. I'm hoping I can say, "problem solved." Thanks guys!
 
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