Gas leak of unknown origin

It was warm here in Baltimore this weekend so I decided to break the bike out of it's winter prison, (probably prematurely). I had planned to pull the carbs anyway but needed to ride it from storage to my shop. After hooking the tank up I noticed a good amount of fuel leaking all over the carbs and down onto the ground. I didn't see any fuel in the airbox nor coming out of the overflow tubes. I pulled the carbs, replaced the needles and dry set the float heights. I hooked the tank up to the leveled carb bank and opened the petcock. I should note that the petcock is actually a fuel valve which I bought from Chacal and only has on/off/reserve. The fuel appears to be coming out of the rotating, metal fuel line between the carbs but it is really hard to tell if that is the only spot. Sometimes I think it is also coming from the bowls.

-If the needles are seating correctly, that should be enough to prevent overflow, correct?
-What are the parts that can erode and lead to leaking between carbs?
Is this the "throttle shaft" or is that the channel above?

The petcock is new this season and I never noticed the leaking before (and it would have been hard to overlook).

-Is is just the added pressure from the gravity fuel valve which has shed light on the issue?

When you ride there is always the risk of going up in flames, I just don't want it to happen before I leave the driveway.

Thanks,
Marshall

 

Seek and ye shall find...

"
FUEL PIPE O-RINGS:

If you find it necessary to replace only the #2 & 3 carb bodies, whle the rack is apart, you'll want to replace the fuel connector pipe o-rings:

mmm1) OEM and Aftermarket Hitachi fuel rail Connector Pipe O-RING.....all fours carbs share a common fuel supply, and this fuel supply is distributed to each carb via a brass or aluminum tube that connects one carb to another. These tubes fits into a machined bores in the carb base, and the tubes are sealed in their bores with these rubber o-rings. NOTE: original seals were "D-rings" rather than "O-rings", but are now serviced only as o-rings (both OEM and replacements), but are the correct shape and firmness to provide a leak-proof fit. You will only be able to access these seals if you break the carbs out of their rack! (and if you do break the rack, you need to replace these seals). Aftermarket seals comes in your choice of either a lower-cost Buna-N material, or a longer-life Viton material. Either one will work just fine and last until the next time you take your carbs apart!

The viton material is much harder than the Buna-N material and the use of the viton seals requires quite a bit of effort to install the connector tube into the carb fuel port bores!

- Use 2 seals per tube, or a total of 6 seals per entire carb rack, for HSC32 series carbs (XJ650 except Turbo, XJ750 all).

- Use 2 seals per tube, or a total of 10 seals per entire carb rack, for HSC33 series carbs (all XJ700 non-X models).


HCP92 OEM Hitachi fuel line Tube O-Ring, each:
$ 1.50

HCP92SET6 OEM Hitachi fuel line Tube O-Ring, set of 6:
$ 7.50

HCP92SET10 OEM Hitachi fuel line Tube O-Ring, set of 10:
$ 9.00


HCP2421SET2 Aftermarket Hitachi Buna-N material fuel line Tube O-Ring, pair:
$ 2.00

HCP2421SET6 Aftermarket Hitachi Buna-N material fuel line Tube O-Ring, set of 6:
$ 4.00

HCP2421SET10 Aftermarket Hitachi Buna-N material fuel line Tube O-Ring, set of 10:
$ 6.50


HCP2420SET2 Aftermarket Hitachi Viton material fuel line Tube O-Ring, pair:
$ 2.50

HCP2420SET6 Aftermarket Hitachi Viton material fuel line Tube O-Ring, set of 6:
$ 6.00

HCP2420SET10 Aftermarket Hitachi Viton material fuel line Tube O-Ring, set of 10:
$ 8.50"

That answers some of my questions,

Thanks Len!

 

The same leak has occurred on my XJ. The fuel rails that connect the fuel passages of all 4 carbs have o-rings on that that help them seat and still be able to move around without leaking.

I believe that the leak you are noticing is coming from the fuel rail between carb 2 and 3, as that is where the fuel line from the petcock comes in and movement from connecting and disconnecting the tank probably shifted the fuel rails around and is causing them to leak. I ordered replacement o-rings from Chacal and am waiting to install them to fix my issue. It's worth giving it a try, as the entire set of o-rings is only $9 or so.

 

Well, there you go. Chacal beat me to it.

 

yes, he's thorough and quick, that Chacal. I am ordering the same set of o rings and probably a bunch of other stuff that should be replaced while I have the carbs broken apart.

thanks

 

Are your floats properly adjusted? I had that problem with mine after rebuilding and I had to adjust the float settings. If they don't close when the bowls are full, the excess gas runs out all over the place. Just a thought.

 

That thought crossed my mind. I did the clear hose test on all four carbs and it looks like the fuel level is low in the bowls, slightly. If that is the case I think the valve needles would close prematurely with less fuel wouldn't they? Thanks.

 

Yes, you're right. I guess it's back to the old drawing board for clues.

 

Would that cause gas to run out the number 2 and 3 carbs? Because that's the issue I'm having right now. Or is this also a O-ring deal? This may be a dumb question, just new at working on bikes.

 

Gas will likely run out of any carb that has a float adjusted too high, as the carb in question's float never closes the fuel supply off and the excess runs out the carb. If your floats are all adjusted properly, then it sounds like a gasket/oring type issue. To check your floats, there are many topics posted on how to do it, but you'll likely need to remove the carbs to do it. Unpleasant, but necessary to do it right.

 

Check your float needles. I had a leak driving me crazy that looked to be a float height problem. I looked at the float needles closely and noticed that the rubber seemed to have shrunk.

Installed new needles, checked the float heights again for good measure. Just a few tweaks on one of the carbs, bada bing, no more leaks.