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Old 06-20-2002, 07:19 PM
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Leaking Petcocks - Several Solutions

Leaking Petcocks
Several Solutions

David Hansen
A number of owners reported leaking fuel petcocks. The big danger of a leaking petcock is that fuel will overflow the carbs and get into the cylinders and finally, into the case where it will mix with the oil with disastrous results.

Most owners found that they eliminated leaks by disassembling the petcock and bending the little round retaining washer that sits under the face-plate. This puts more pressure on the valve and keeps fuel from leaking.

Be careful not to bend the washer too much. If too much pressure is applied, the vaccuum valve may not hold open the petcock at high RPM. This can lead to fuel starvation

In my case, however, the problem was that one of the 4 holes in the rubber diaphragm had a small tear. As a result, even with good contact between the valve and the diaphragm, fuel would leak. Fortunately, the diaphragm is symmetrical and one of the holes is designed to sit over a little centering peg. So I turned the diaphragm over and put the leaking hole over the peg so that it wasn't in contact with flowing fuel any longer.

Paul Streit reports that the rubber diaphragm is still available from Yamaha at a reasonable cost (<$10), so consult your local dealer for the proper part #.

Jeff Hall
Just wanted to share with everyone that K&L makes a fuel petcock rebuild kit for XS11's. The part number for my 79SF is 185100 and comes with all the o-rings and gaskets plus the vacuum diaphram. The kit will rebuild both petcocks and it cost $32.00.

Paul Streit
The gaskets that you need for the petcock swivel are some of the few of the gaskets that you can get. The Yamaha item # is 1j7-24523-00-00 on the tag is also a bin # 17-104-k-01-1. I got this off of an extra set of gaskets that I bought I has a leak and I rotated the gaskets and the leak stopped.

Bill Kingson
I had a leaky petcock on my '77 GS 750 (only one on this tank). Sloan's in Murfreesboro, TN, was able to get me a replacement but it took a couple of weeks. While awaiting delivery I made the following no-nonsense repair.

For about $8 I picked up a generic in-line brass fuel valve from the local auto supply. With a piece of 1" x 1/16" x 1.5" iron I made a cover plate for the petcock mount. Then I drilled a 1/4" hole and soldered in a short piece of 1/4" copper fuel line. Hooked in the fuel line and it was done. Total cost under $10.

This is strictly an on/off arrangement, but it's rock solid and doesn't leak a drop. I just have to remember to turn the gas valve on for start ups and off for shut downs. It's a small bother, but it sure beats leaks! The replacement petcock arrived about two weeks ago and I haven't bothered to install it yet. I guess I'll wait until this tank's empty and go for it.

The valve I used had compression fittings at both ends for attaching the copper fuel line. I attached one end of the valve directly to the tube on the adapter plate on the tank. This way the valve is hard mounted to the tank and makes it easier to operate.

On the other end of the valve I just used a piece of copper tubing long enough to hold the flexible fuel line securely. After my initial assembly I found that there wasn't quite enough room to attach the flex line without kinking it. Be sure to check your clearances before you make anything permanent.

I used some gas-proof sealant on the adapter plate when I mounted it up. I didn't want to risk fouling the gasket that went with the petcock. The stuff I used was a non-drying formula. It cures over night, but never really hardens. This was new to me. When I checked it out after 24 hours, I thought it hadn't worked properly. Then I read the fine print on the tube more carefully! No leaks anywhere!

Since I only intended to do a temporary fix, I used the cheapest valve I could find. It works great, but it takes several turns to open and close it fully, like a faucet. For a couple of dollars more I could have had one that had a lever and required only a half turn to open and close. If I were to do this again I'd use one like that.

MOST IMPORTANT. Once this mod is done you have to be sure to turn off the valve(s) EVERY TIME YOU SHUT OFF THE ENGINE or you'll flood out the carbs (unless your needle valves are perfect). It's just like leaving the stock petcock in the PRI position all the time. (Don't ask how I know!)

Jim Mercer
Pingel makes adapters that will fit, they also make a boat load of
petcocks. The adapter plate is 3/8" thick, 3/4" wide and about 2" long. It's chrome plated and has a 3/8" NPT hole in it with a counterbored hole at each end for Allen screw mounting to the tank. comes with gasket also. The bolt hole spacing is 34mm, C/L to C/L. Adapter # A1602C. This fits the tank on my 79SF. If Standards have the same spacing this will fit them also.

The petcocks I have are dual outlets with no reserve...They have single outlets with reserve or dual; they also with make whatever you need. They all come chrome plated and are really good looking. You need to get internal height measurement of the tank from the petcock tank opening to verify that their filter screen will clear. I didn't have that problem because mine doesn't have a reserve valve, making the filter screen very short. The petcocks I bought cost $70.20 each and I the plates are $9.65 each. Remember these are not set up for vacuum.

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