How to Do 2-Stroke Leak Down Test - Page 2
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  1. #11
    PWCToday Guru E350's Avatar
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    Re: How to Do 2-Stroke Leak Down Test

    Myself! You are brilliant. There have been a couple of symptoms I observed that are consistent with a blown head gasket. For the last 4 or 5 trips, the exhaust has been "hotter" and more gaseous than usual -- less "water full" than usual. But I don't have enough experience with these things to know what the exhaust is normally supposed to look like. I had added some Red Line powersports fuel treatment in the gas and just assumed that it had cleared some carbon out of the cylinders, and was in fact now running correctly. I will try your test this morning and report back.
    Last edited by E350; 10-08-2017 at 10:39 AM.
    Learning Slowly...

  2. #12
    PWCToday Guru E350's Avatar
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    Re: How to Do 2-Stroke Leak Down Test

    Ok guys, just now got back to the X-2. I unbolted the engine and removed the mounting plate but left it in the engine bay but was able to turn it around to look at it while pressure testing.

    Result: soap bubbles are negative everywhere except for where my homemade block off kit fits on the carburetor manifold. I cannot even hope to do a leak down test without a proper block off kit.

    ANY RECOMMENDATIONS FOR WHERE/WHOM TO PURCHASE A BLOCK OFF KIT FROM FOR A 650?
    Learning Slowly...

  3. #13
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: How to Do 2-Stroke Leak Down Test

    I make my own from an old innertube. Just trace the carb base gasket and punch out bolt holes only, install carb. Do the same on the exhaust manifold to headpipe joint. The innertube seals them up nicely.
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
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  4. #14
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: How to Do 2-Stroke Leak Down Test

    Quote Originally Posted by E350 View Post
    So, I was riding the '88 X2 650cc this afternoon WOT and it was doing what I have been complaining about, mainly it loses rpm
    when I pull the throttle the last 1/8 or so to the throttle stop (so I back off on the throttle some and the rpm's increase).
    That is normal. I have worked for a famous owner/tuner who welded a tab
    on the throttle cable stop, based on water and dyno testing so the throttle
    butterfly stops at 7/8's throttle.

    Your set-up, including impeller could affect it. What is it? do you have any
    modified stock parts, like the pipe mod?


    Bill M.
    Horsepower == Speed, RPM != Speed



  5. #15
    Resident Guru JC-SuperJet's Avatar
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    Re: How to Do 2-Stroke Leak Down Test

    Rubber Expansion Plugs are cheap and work well. Available at any Hardware Store near you.

    Rubber Expansion Plug.jpg

  6. #16
    PWCToday Guru E350's Avatar
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    Re: How to Do 2-Stroke Leak Down Test

    Thanks JC SuperJet, but the holes are oval, not round...

    I found these, but I don't facebook so I pm'd him:

    http://www.x-h2o.com/index.php?threa...-seals.175210/
    Last edited by E350; 08-26-2018 at 02:00 AM.
    Learning Slowly...

  7. #17
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: How to Do 2-Stroke Leak Down Test

    Quote Originally Posted by E350 View Post
    Thanks JC SuperJet, but the holes are oval, not round...
    You are doing it the hard way, and making mistakes that will cause an incomplete test.


    You have the resources you need in Sacramento to make your own plates from rem stock,
    and purchase 1/8, 3/16, or 1/4" neoprene rubber sheet in Sacramento. Or order it from
    Mc Master Carr. I googled it to find the resources.


    Bill M.

    you also have to leave the spark plug in the cylinder which you do not have the leak test adapter screwed into.

    It is also noteworthy that the piston in the cylinder you are testing does not need to be at top dead center on
    the compression stroke. (Because you are not testing the piston rings sealing ability with the valves closed on a
    4-stroke engine.

    Rather, you are testing the entire crank case's ability to seal in pressure in a 2-stroke engine, which has no valves.
    That is why you need to test each cylinder (not just the front) at Bottom dead center,
    with exhaust and transfer ports wide open.

    You can also make a better air pressure/vacuum port with an old spark plug, a brass fitting
    or copper tubing, and JB weld.
    BM.
    Last edited by wmazz; 08-26-2018 at 02:09 PM.
    Horsepower == Speed, RPM != Speed



  8. #18
    Resident Guru JC-SuperJet's Avatar
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    Re: How to Do 2-Stroke Leak Down Test

    Been able to plug and seal all Intake and Exhaust Holes (SeaDoo, Yamaha & Kawasaki) with the simple and cheap Rubber Expansion Plugs.

    The Rubber in the Plugs expands and conforms to the the shape of the hole and will seal even oval ones.

    No need to spend time manufacturing custom blind plates and gaskets.

  9. #19
    PWCToday Guru E350's Avatar
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    Re: How to Do 2-Stroke Leak Down Test

    JC-SuperJet: Thank you. I have to drop by Home Depot today anyway so I will look for those plugs and report back.

    wmaz: I have 1/8" neoprene rubber in sheet which I bought from Capitol Rubber for this project last October. But it is too stiff to seal properly. I will swing by there today and see if they have some less dense sheet product.

    As far as the appropriate way to do the test. I will plug up the pulse hose and use the spark plug hole. Is this the testing process?

    1. I take both spark plugs out to reduce resistance;
    2. then rotate the cylinder to be tested to dead bottom center;
    3. then put in the other spark plug;
    4. then put in the spark plug which has been modified to accept the input of air (i.e., for
    pressure test) or the removal of air (i.e., vacuum test); and
    5. put ____ lbs. of air into the cylinder and wait ___ mins to see if ____ air pressure reduces to ___ lbs?
    6. remove ____ of air from the cylinder and wait ___ mins to see if ____ vacuum stays at ___?
    Learning Slowly...

  10. #20
    Resident Guru JC-SuperJet's Avatar
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    Re: How to Do 2-Stroke Leak Down Test

    Expansion Plugs are found in the Plumbing Aisle. Buy an assortment.

    My leak-down tests are basic so you need to ask wmazz about his test procedure.

    I prefer to use the Pulse line.

    Just to be clear, I always bolt/torque on the Intake and Exhaust Manifolds with new Gaskets to the Engine.

    Then there is one round Exhaust opening to plug and two round Intake Manifold openings to plug.

    Clean, degrease and dry the Exhaust and Intake Manifold Openings. Install the Expansion Plugs Dry and hold the top Washer while tightening so it doesn't rotate during tightening.
    Last edited by JC-SuperJet; 08-27-2018 at 12:09 PM.

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