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Leak down test

Started by grasshopper, December 24, 2007, 02:04:17 PM

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What do you guys use to plug up the exhaust port and the intake port when doing a leak down test on a dirtbike? I'm trying to do a leak down test on the KX250. I have the tester but for the life of me I can not plug up the exhaust or intake air tight.

Protein Filled

2-stroke? I have a kit from Motion Pro. It uses these plugs that expand when you turn them with a wrench. You can see it at:

But I am sure you could go down to the hardware store and find something that would work. Also, maybe a marine supply store would have them as well, to keep water out of a boat. Maybe something like these:

Edgar Dorn #81 - Numbskullz Racing, Mason Racin Tires, Michelin, Lithium Motorsports

Don't give up on your dreams! If an illiterate like K3 can write a book, imagine what you can do!


Apply the tester and then turn the engine toward TDC with a wrench, you probably won't be able to get to TDC but you will cover the ports. The only thing that this will not test is if you have a lot of taper in the cylinder. 

One BIG warning, DO NOT position the engine at TDC and then apply the tester, the odds of being at EXACTLY TDC are infinitesimally small and things are going to fly.
Paul Onley
CCS Midwest EX #413


Go here :

Under find products (left column) type in test plug. This will give you an idea of the type of plugs for which you are looking.

Remember you do not need much pressure, something like 5 psi max.
Brian McLaughlin
Donate at
2 strokes smoke, 4 strokes choke