Leaking Fuel

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    Hi guys, I’m looking for some suggestions how I might solve the above issue!! My 750 is just about finished after a lot of work but I just can’t seem to stop a leaking fuel problem. The carbs have had complete new jet kits and new floats but when the bike sits idle with the fuel switched off, it persistently drips fuel, which seems to be coming from the bottom of the left hand carb. I think it may be coming out of the overflow and running down the carb body but it is a real pain in the proverbial!! If I leave the fuel on and put bike on side stand, the fuel just flows out! The bike also runs rough below 2000 revs. Any suggestions before I strip the carbs (again!!)


    Because of the way you describe your problem and the work you have done my thoughts are to the left hand float which appears to not be shutting the fuel supply off. That could be 2 things;

    1. The float valve isn’t doing it’s job

    2. The float level is wrong

    My money is on float level




    I had a similar problem and it turned out to be the diaphragm’s were holed


    I’d look exactly where KK advises, float levels, and the valve. It only takes a little bit of crap in the valve to stop it seating, sometimes (and I’m sure you will have tried this) a little tap on the carb will dislodge it and stop the leak. Looks like a carb strip is inevitable at this stage.


    Hi all,

    I agree and go for the valve as well. The mentioned tap / hit to the carbs is essential 😉

    I am doing a lot of work at different twins and the LTD carbs.
    Especially after a full cleaning session where everything is checked and adjusted, there is no fuel in the bowl, of course.
    After fitting the carbs back again and opening the fuel cock (PRI position) the fuel runs into the bowl and the floater should swim and shut of the fuel. If the bike is on the side stand, the valve may stick in the open position leading to leakage.
    I use to keep the bike upright / vertical and then open the fuel cock.
    Fuel is running into the bowl and the floater starts to swim. During that time (approx 10 sec) I always tap the carbs with a plastic hammer, a piece of wood or just with my hands a bunch of times. That typically cures that issue.

    If there is a leakage after that “ceremony”, dismantle the carbs again and check the stuff around the valve (valve itself, seat, floater, floater setting / fuel level).
    Measure the weight of the floaters. They can be untight and filled with fuel which stops them from “swimming”. Dirt at the valve and seat may also cause that leakage.

    To test that without to much work you can drain the bowls until empty. Keep the bike upright and have a “hammer” in your hand. Open the fuel cock and often tap the carbs.
    Leave the cock open and wait and see if the leakage is gone or still existing.

    Hope that helps 😉

    Cheers, Michael


    Thanks guys, I’ll give these things a go. I have tapped the side of the carbs before and this seemed to stop it temporarilly but the problem is now constant and tapping does not work. It leaks petrol on main stand as well as side stand…


    I’d definitely go for float bowl shut off valves then

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