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Where is this fuel coming from

  • Thread starter Thread starter CodyLHen
  • Start date Start date
C

CodyLHen

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Ok let me get everyone up to speed. I had a fuel leak coming from some where in the carbs. I went ahead and took the carbs apart. I replaced all the o rings with the kit from bikecliffs and cleaned the carbs really good. I bought new intake boots. I also rebuilt the petcock. This was especialy a pain because the kit that I got did not work. The o ring on the diaphram plunger thing seemed to small so a replaced with a slightly larger one and a new spring and now the petcock works great. I also put a on off valve in the line just in case my petcock does go(i've heard enough about hydrolock and I dont want to deal with that). I have know put it all back together and synced the carbs up. It runs great but as I was examining the carbs after my ride I noticed that fuel was still leaking. The best way I can describe it is sweating because it is very slow. I thought maybe I dident tighten the float bowls enough but the fuel appears above as well as bellow the bowl(oh i do have new gaskets too). I can't figure out where its coming from. I thought sence the petcock and on off valve were in place that the fuel would not be able to flow. I have the tank off and the clear fuel line still has fuel in it and does not seem to go down but the carbs continue to leak. Anyway, I will stop my rambling. If anyone has had this problem and have some suggestions that would be great. Thanks
 
Hi,

Hmmm, I dunno, but I'll hazard a guess. Is your float height set correctly? Many have reported trouble with petcock rebuild kits and end up just buying a new one. What bike are we talking about? Please put it in your signature so we don't have to search through your old posts to find out.


Thank you for your indulgence,

BassCliff
 
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My bad. Its a 1977 gs 750. If the float height is set incorrectly, wouldent the fuel come out of the overflow and not somewhere in the carb.

I dont think I will need a new petcock though, the o-ring that I bought at a hardware store is working far better than the one that came with the kit. The ring that came with it was a #61 and I ended up using a #36. I think that they should send a replacement spring in the kit. Mine was worn out so I replaced with slightly larger spring for better pressure against the diaphram.

If its not the float height my guess is that the needle and valve probably need replacing. Again though, I figured if they were not holding back the gas that it would end up coming out of overflow.

I guess the overflow could be pluged in the bowl itself. This is hard to beleive given that I dipped and cleaned them. I blew through the tubes already and they were clear.
 
Does anyone know the float height of a vm29 carb. The manual that basscliff posted does not have it or I'm reading it wrong. Unless its the vm28 - 49 measurement. I want to be sure. Thanks.
 
Could you have a small crack in the carb body or in one of the tubes that join the carbs together? Is it leaking from one spot or are all the carbs leaking?
 
almarconi

Could you have a small crack in the carb body or in one of the tubes that join the carbs together? Is it leaking from one spot or are all the carbs leaking?
Click to expand...

It seems like its running down from somewhere else and collecting at the #1 carb. I will be putting it back up on the center stand to get a proper view. I was not able to last night because I really struggle getting it on the center stand alone.

As far as cracks go, I did not notice anything like that when I had them apart, but to be honest I was not looking for cracks. Has anyone had this happen before? Where do cracks commonly form? The tubes between the carbs did look good though. When I changed the O rings I had a good look at them.
 
One easy thing to check or dismiss.

I thought my floats were sticking on my GS1100 because every now an then I would see a couple of drops of what I thought was gas on my shift plate cover. One day I noticed that my relatively long breather hose which I run between the battery box and the engine down to the ground had coiled sideways and upwards and the condensate was collecting in the tube and being blown out on start up. Where does your blow by go?

Just a thought. Hope its that easy
 
HI Mr. CodyLHen,

According to the VM carb rebuild guide on this site (there's a copy on my site too), the float height should be 24mm. There's also a little information in the carb spec thread sticky at the top of the Tech section. Let us know what you find.


Thank you for your indulgence,

BassCliff
 
others may disagree here, but my carb bowl gasket leaked a bit...well, more like it sort of bled a little...for a little while when i put new ones on last year....looked like a small leak. took me a couple tries to get it to stop. maybe?
 
greg78gs750
others may disagree here, but my carb bowl gasket leaked a bit...well, more like it sort of bled a little...for a little while when i put new ones on last year....looked like a small leak. took me a couple tries to get it to stop. maybe?
Click to expand...

I think this may be the case. The leak is so slow that it does not really leak more unless i wipe it away. Bleed is exactly the way to describe it. My big plan is to buy all new stainless still hex head screws and lock washers. I will be able to torque them down a little better since the current screws are getting worn out. I also mixed some of the top and bottom bowl screws up(dident realize they were different lengths) and since the bottom are longer the shorter screws might not me securing the bowls tight.

On the up side I went out riding and it ran so good I almost shed a tear. Its like a night and day difference with the new boots. When I first got it, it was fun to ride but I kinda drove it like a old 4 cyl pickup keeping the revs low because it dident rev up good. Now, all synced up, it revs up great.

I drove it to my local shop where I have been getting parts and advice and they dident seem to concerned about the leak. It was suggested to keep riding it for a week and see if it seals up. I think they were impressed that It ran so well. Being my first time ever rebuilding any carbs It made me feel pretty darn good.

This is a great bike and It would not run as well as it does without this web site. Happy riding everyone.
 
I wouldn't be at all surprised to find out that one of the gaskets has a slight leak to it.

If you've rebuilt the petcock AND installed an on/off valve, then that leads me to believe that it's not the petcock letting any extra gas down into the carbs.

If all else fails I'd suggest trying that needle valve. I had a huge problem with leaking gas on my Ninja 250...turned out that one of the needle valves had gone bad and when I replaced it, I've never had an issue since then.
 
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