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Thread: air leaks

  1. #1

    air leaks

    ok ive rebuilt the 951 gsxl motor. ive rebuilt both carbs. and due to the slow runaway (it doesnt quickly runaway, just slowly but she gets up to 4900 and i choke her down or shut her off) the consensus is an air leak, my question is whats the best way to locate said air leak? anyone got any tried and true tricks? thanks

  2. #2
    MSX 150 guy lives on Mr. GP1800's Avatar
    Join Date
    Jun 2010
    Milwaukee WI
    Did you pressure test the motor after you rebuilt it? Seal off the intake and exhaust manifolds and pump it up to see if it holds pressure?

  3. #3
    Is this out of water only? You'd better pressure test the engine to make sure. Manifold block off plates are available.

  4. #4

    Join Date
    May 2011
    Central Coast California.
    You can buy a block off kit or I just went to the hardware store and bought a 1/8" sheet of neoprene rubber. It looks like a piece of conveyor belt and must be smooth on both sides. Use your carb base gaskets or throttle body gasket and the gasket between the exhaust manifold and pipe as a template to make the block offs. It should be the same as the gasket but without the big hole in the middle. You also will need some brass fittings and a tee on one side of the tee you need a schrader valve like on your car tire, on the other side a barbed fitting to attach a piece of hose and on the last side of the tee a low pressure guage in psi. The process is to connect the hose from your new guage to the pulse line fitting on the engine that would connect to the fuel pump on the carb then very slowly increase the pressure to 8 psi, do it very slow and only go to 8psi if you go too fast and too much pressure you can blow out the gaskets and seals. It should hold the 8 psi for 10 minutes on a new engine. If the pressure drops use soapy water or something like 409 and spray every part of the engine and even your newly made guage. You will see lots of tiny bubbles or foam forming at the point of the leak. I am not sure if leak down kits are available but this test should be performed any time an engine st taken apart and reasembled. I think Group K used to sell them.

  5. #5

    Join Date
    May 2007
    Have you rebuilt the carbs ?? the low and high speed adjuster screws have little o/rings on them but they are different sizes.if you get them mixed up it will leak 100%

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