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  1. #1

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    Yamaha suv leak down pressure test result

    Hi, am currently working on rebuilding the engine, did a leak down test. So many post did it different ways, I have no idea if I did it right. Some said must hold 6 psi for 10 min . some said 10 psi and ok to loose 1 psi per min.

    Ok, here is what i did. I put in 10 psi. After 10min it drop to 9.5psi and 30min later 7.5psi left. I then release the pressure. Is this test result good? Should I look for leak? Thanks


  2. #2
    urugol's Avatar
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    That's a very tight engine. No leaks there.

  3. #3

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    Thanks for the post , it is ready to go in the hull.

  4. #4
    Yamaha artisan Cutlass's Avatar
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    I agree. sounds like its nice and sealed up

  5. #5
    Birdgod led me to this and one other thread on leak testing. My local mechanic told me that I did not need to do a leak down since we just did a top end job. I took the advice of this forum and did one anyway by:

    1. Buying some shower pan liner rubber sheeting from Lowe's and tracing the outer shape of the carb base gasket and the exhaust base gasket on it. Cut them out and cut bolt holes in the rubber to completely seal off the carb/exhaust sides.
    2. Used a thin layer of blue RTV silicone on the exhaust and carb holes to make sure the rubber would have a complete seal around them.
    3. seated the carbs down and the exhaust base down and torqued the bolts/nuts to spec.

    It worked like a champ.

    4. put a golf T into 2 of the 3 pulse lines which were attached to the engine (not the carb) and threw a worm clamp around the golf T/pulse tube to seal that off.
    5. On the middle pulse line, I connected in the pump off of my small pancake compressor (pictured).
    6. Slowly squeezed the pump handle to insert 6 psi

    BUT.....it never quite made it there. A loud "hisssssssssssssssssssss" came from the bottom of the crank case to remind me that the devil himself resides in the bottom of 2 stroke motors

    The crack was hiding right under the motor cradle where we couldn't see it. Soooo glad you guys gave the high recommendation to do the leakdown test. My plan was to throw this brand new top end into business and I am sure that chunk of shrapnel from the blown piston would have made another appearance or the air mixture would have burned me up all together again. Unreal. Being a weekend warrior garage mechanic I always assumed that buying a ski with a blown motor would mean that a oil line had popped off and the thing burned up due to that. I never really thought about what happens to the piston chunks after the fact. Anyway, I learn...therefore I am.

    If anyone else ever reads this after doing a top end job or more...DO A Leak Down PRESSURE TEST!
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  6. #6
    Yamaha artisan Cutlass's Avatar
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    Nice find! I'll never build a 2 stroke motor again without a pressure test. Its so critical.

  7. #7
    Amen! +1

  8. #8

    Leakdown technique question

    On the 1200 Non-PV out of an SUV, the exhaust side looks like this:
    Since the exhaust manafold all boils down to this muffler outlet, can't I just leave this all in place and just block off this exit with a gasket or plate? If that is the case, then I should be able to just take the carbs off and block off that side as well with a modified plate (probably just take the base plate on the carbs and use that to lock down a chunk of rubber to block it off??? Does this seem like it should do the job anyone?Click image for larger version. 

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  9. #9

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    Yes, you can just block off where the red arrow point to. and the carb side that work too. well at least that is how i did mind.

  10. #10
    Yamaha artisan Cutlass's Avatar
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    Thats what I did




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