Carb Fuel Fitting Leak

Hey all,

I’m almost finished with a basket-case ‘79 KZ750 C3 that I’ve been working on for the last few years. Unfortunately, I’ve hit a surprising issue that has me stumped.

I just finished rebuilding the carbs, checking the float levels, and syncing them. Bike finally runs, and runs well, but I’ve noticed I’ve got a leak where the fuel hose from the tank connects to the carbs.

Gas is seeping out from the fuel hose connection. I’ve tried the stock spring type hose clamps and band clamps with no success. I’ve tried various sizes of fuel hose, same result each time.

Anyone ever run into this issue before? I think the problem is the grooves on the fitting are too close together for my clamps to make a good seal (the bands of the clamp are wider than the space between the grooves on the fitting).

I’ve attached a photo of the fitting so you know what part I’m talking about. I’m sure I’m missing something simple, but it’s been driving me crazy!

Thanks!

The fuel T between the 2 carburetors probably has o-rings that need replacing.

Is it leaking between the "hose and fitting" or is the fitting cracked where the two parts of it are joined?

The barbs look fine and should seal without a clamp with the proper size hose. I bet one of the two possibilities mentioned above are the culprit.

That fuel Tee is made of aluminum, and the cross drilled feed nipple is press-fit into the main body.  I've seen some similar Tee's, china made, leak at the press fit.  And on the fuel Tees that I've seen, the O-rings are inferior pieces and should be replaced. 

I make a lot of fuel Tee's from scratch, but more recently, for the dual feed VM26 carbs, I buy china made brass Tee's made for a center feed application (like this one), and modify them for use in dual feed carbs.  I do this because they are decent quality, and I haven't found any (cheap) dual feed Tee's that are a better value.  Being that they are brass, they are more sturdy than aluminum, and I haven't had any press fit created fuel leakage (yet.)    I always replace the O-rings also.

Bottom line with this issue, you need to study closely to find the exact location of the leak.  Regarding fuel line, I buy Suzuki line for GS bikes.  It's 7mm ID, and stretchy, and doesn't need a clamp.  The package comes with about 5' worth, too.  Good stuff.

Thanks for the ideas guys, I’ll dig back into it and see if I can figure it out.

It’s definitely leaking from where the fuel hose joins the T. I took the carbs off the bike to watch more carefully. When I turn the fuel supply on, you can see air bubble all around the bottom of the fuel hose followed by fuel seeping slowly out.

With no clamp, a lot of fuel seeps out. With a tight clamp, the leak is a lot slower.

I hadn’t considered that the T itself might be cracked, that’s definitely a possibility.

I use the plastic version and soak them in gas for 24 hrs before installing to get them to swell up a bit.

Some skrink tube will fix the leak instantly!

 
 

Good idea about the shrink tube, I bet that would fix it.

The problem did indeed turn out to be a crack in the T fitting. I had a spare, so I went ahead and replaced it. No more leak, works perfectly now! 

Thanks again for the suggestions!