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Carb leak (or fluid on carbs)

  • Thread starter Thread starter Joe Garfield
  • Start date Start date
J

Joe Garfield

Guest
I've got fluid accumulating on the carbs. I tried cleaning it up and periodically stopping to see where it originates, but that's been unsuccessful; I don't see anything dripping when the bike is parked and I've got to ride maybe 100 miles or more before I notice much. I can't tell where its coming from. Petcock is new and doesn't appear to be leaking and I don't see it coming from the choke rod, but I could be missing it. Maybe it's coming from the float bowl gasket and dripping/splashing? Or is it something else? Carbs have been rebuilt a few hundred miles ago, but still have original diaphragms.

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A couple of those pictures look like it's the float bowl gasket, some of the others look like maybe the throttle shaft seal.

Diaphragms would not make anything leak like that, they never see any gas.

.
 
Those are minor leaks. More like seepage. The debris in the middle may even be some oil residue collecting dirt. I'd wait till winter and do a complete rebuild of the carbs. Check your timing chain tensioner and make sure the oil isn't coming from there.
 
I would consider investing in some new carb holders/orings. They look like the originals and since made of rubber, are not expected to last forever. As far as the very minor gas leak, gas accumulates in the # 1 & 2 carb bowls when the bike is on sidestand. I would invest in new bowl gaskets and it looks like a fuel rail may be seeping which means the assembly has to come apart if it bothers you. Note you don't get any drip on the #4 side because this stuff likely happens when the bike is on sidestand as I noted.
 
Joe Garfield said:
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In this photo it looks like there is a breather pipe missing from that plastic fitting just to the left of the yellow circle (unless it is the fuel supply T-piece?). Usually the breather pipes go up and over the airbox, extending some way down behind the airbox.
 
I think the bowl retaining screw should be more fully engaged with the carb body casting, even sticking up a bit.
 
The four screws that hold the bowls on are M5x16. Yours are M5x12 or 14 asd not quite as long as the originals but they are not the reason for the small leakage. They catch enough thread to be tightened securely.
 
2BRacing said:
In this photo it looks like there is a breather pipe missing from that plastic fitting just to the left of the yellow circle (unless it is the fuel supply T-piece?). Usually the breather pipes go up and over the airbox, extending some way down behind the airbox.
Click to expand...

Good catch! Thank you. I've been confused about vent, vacuum, and breather hoses. Looking again at BikeCliff's site, I now realize I don't have vent hoses hooked up. That seems a likely culprit for the fuel on carb #2.
 
geol said:
The four screws that hold the bowls on are M5x16. Yours are M5x12 or 14 asd not quite as long as the originals but they are not the reason for the small leakage. They catch enough thread to be tightened securely.
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Thanks - I see it now. I'll check that #1 is tight enough. The carbs were fully rebuilt and got some new hardware. I believe the gaskets are all new but the bolts could have loosened up a little.

The bike has a really gassy smell and I think is 'using' a little extra fuel. My reason for posting this was just to make sure there weren't signs of the carbs not shutting off or something, but it sounds like were mostly just seeing seepage (or missed breather hoses). This bike still has a lot of other maintenance needs, and being my only bike I don't want to start pulling apart carbs unless its really necessary. I will take care of the breather hoses though... :)
 
When the carbs were rebuilt/cleaned did you break them down and replace all the various O-rings, including the ones on the interconnection tubes between the carbs? Was the fuel level verified using the clear tube method?
 
Nessism said:
When the carbs were rebuilt/cleaned did you break them down and replace all the various O-rings, including the ones on the interconnection tubes between the carbs? Was the fuel level verified using the clear tube method?
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I'm not totally sure (I forget what was in the rebuild kit); and no, float height was measured but fuel level not checked - I will do that.
 
Joe Garfield said:
I'm not totally sure (I forget what was in the rebuild kit); and no, float height was measured but fuel level not checked - I will do that.
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Did you ungang all the carbs from the joining bars? Doing so is the only way to replace the fuel transfer tube O-rings. Those are the O-rings that are most routinely hard and brittle, thus failure to replace them can lead to leaks. Also, as the float needles age and the springs get weak it's critical to check them using the clear tube method to be sure the fuel level is correct. The float height check is just to get them close, sort of like the difference between bench sync and vacuum sync.
 
Yes, carbs were fully broken down to individual components, soaked/cleaned, and rebuilt. I feel like old, crusty o-rings would have been replaced but it was over a year ago and I can't remember. During the off-season I'll check things out more closely.

And thanks for reminding me about the float level. I was gearing up to do an idle mixture check, but it seems like I should check/adjust the floats first.
 
Ok so I'm back at this problem. After cleaning things up, the bike has sat for awhile and was transported. I just started paying attention to it again and noticed a good amount of fuel on #1 and #2 and decided it's time to start pulling things off.

I noticed a lot of fuel around the intake port - I thought that was a little odd. See pic (link).

The tank is sitting in normal position with both petcock hoses in a clear container. It doesn't look like anything is dripping but I want to give it another day (check when I get home from work today). The petcock was recently replaced with OEM unit.

I removed the carb assembly with the float bowls full of fuel. If I tipped the carbs slightly, fuel visibly seeped from #2 where the float bowl meets the carb body.

The carbs have been cleaned and rebuilt. I do recall seeing a slight tear or hole in one of the diaphragms, so my thought was to replace all the float bowl gaskets, and probably replace the diaphragms with aftermarket. I also want to look closer at any O-rings at the carb interconnections.

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The reason I'm saying all this is I plan on leaving the jets alone, and I'm not doing a complete overhaul (although I'll check the condition of the jet plugs while I'm in there). The carbs were fully rebuilt within the past 2 years, but I forget exactly if anything was reused other than the slides and jets/hardware.

I also don't know if the float valve should have stopped fuel prior to it reaching the height of the gasket? I'll inspect the floats and pins and measure the float height, and I'm planning on getting the homemade plug barb so I can measure fuel height.

I assume I'll need help balancing the carbs, again, after this is done (well, after I complete the top-end refresh I'm planning).
 
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It looks like its all coming from the float bowl gaskets. The float bowl screws weren't very tight (I unscrewed them with an Allen ratchet bit and 2 fingers), and the float bowls' sealing surfaces look like they'd been filed at some point. All the leaking was between the float bowl and gasket, not between the gasket and carb. I'll replace the gaskets and either have a shop dress the bowls, or maybe do it myself if I can get a free granite sample or something big and flat enough to work on.

The diaphragm I was worried about (which shouldn't affect a fuel leak) was #2 - two or three tiny pin holes at the crease where it folds away from the groove in the carb. Its hard to justify a new set of diaphragms for that at this point - I'd rather get to the top end refresh and leave the carbs alone until next scheduled (or needed) service. If I had the work space, I'd love to take the carbs apart and refresh some other parts (springs and nylon spacers on starter lever, e.g.) But...I don't.

The petcock is working fine. So the last thing I have to do is check float valve function and fuel level. I can't believe it's proving to be this difficult to find a ready-made tool tool! There's one on Z1Enterprises' website (https://www.z1enterprises.com/fuel-level-gauge-tool-kawasaki-suzuki.html) but it says it's for the VM carbs, which have a different P/N than the BS34 for the drain screw; I've read the BS34 drain screw is 6mm by either .7, .75, or .8 thread pitch. I'll bring one out to measure but I can't spend endless amounts of time on these things like I used to. There are cuts in the threads in the carb so I don't want to try the 'threading a plastic hose' method.

I also need to figure out how to check float valve function. I'm hoping I can do this with the floats still in the carb. I'm basically working in a small space on a garage floor so intricate parts are not as easy to work with.


I guess I'll add in here that there are a few main things I'm trying to address with this and a top end refresh. So these are my main priorities - if something like the diaphragm was a likely cause for any of it, I'd go ahead and replace the set. I don't think it is though, especially since it didn't show up with the carb sync, but that's really more of a guess. I'm sure on some small level it has an affect but I'm assuming it's hidden in the noise of everything else.
1) obviously a fuel leak
2) heavy oil use and smoke
3) one broken exhaust stud
3) vibration - most noticeable below 5000rpm - even after carb sync
 
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