Build your own leak-down tester.

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10/18/2020 3:53 PM

I wanted a leak-down tester and they cost over 200 dollars, so I decided to make my own. I used a solid acetyl copolymer rod and drilled it out and drilled and tapped the holes for the brass fittings. I bought the gauge from Amazon for 20 dollars. Came out fairly nice. Photo
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10/18/2020 4:45 PM

Very cool, congratulations. I did similar a few years ago except I used aluminum that was handy.

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10/18/2020 8:12 PM

Thanks. I wanted to use aluminum, but don’t have the equipment to do the machining. I did all of this with a hand drill and taps.

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10/19/2020 9:36 AM

Great job

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10/19/2020 11:04 AM

Thanks!

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10/28/2020 5:09 PM

Looks good, now please explain how this works ? I always thought these were threaded into the spark plug hole ?

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78 RM250C
79 YZ250F
81 YZ465H
80 MX6 125
81 MX6B 250



10/28/2020 6:45 PM

There are compression testers, compression leak down testers, and crank volume leak down testers. Mine is a crank volume leak down tester. It inserts in the carb boot, where you clamp it into place with the hose clamp. Then you plug the exhaust exit port/hole with a pipe plug. Then you pump air into the device until you reach 5 PSI. You watch the gauge for 5 minutes. It should not leak down much. You can look up the acceptable leak down rate for your 2 stroke.
The compression tester, or compression leak down tester, thread in the spark plug hole.

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10/29/2020 2:54 PM

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2018 KX450F
2005 KX250
2003 KDX 220
1984 KX 80
1982 RM 80
1980 RM 80
1977 XR 75
1969 Honda Mini 50

10/29/2020 5:34 PM

Yes, and that is for above the piston compression leakdown.

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10/29/2020 5:37 PM

Motion Pro’s 2 stroke crank leak down tester. This is why I made one. https://www.motionpro.com/product/08-0071

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10/29/2020 7:42 PM

Dennis_Fitzpatrick wrote:

Yes, and that is for above the piston compression leakdown.

You do understand that if the piston is below the transfer ports you can also test crank seals through the spark plug hole provided the intake and exhaust are blocked off. So not sure why you would think this is only for above piston.

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2018 KX450F
2005 KX250
2003 KDX 220
1984 KX 80
1982 RM 80
1980 RM 80
1977 XR 75
1969 Honda Mini 50

10/29/2020 8:41 PM

So, high pressure air applied to the crank will blow the seals out. If I’m not mistaken, the transfer ports come into play when the piston skirt rises above their openings. Explain your concern.

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10/29/2020 9:39 PM
Edited Date/Time: 10/30/2020 4:05 PM

Dennis_Fitzpatrick wrote:

So, high pressure air applied to the crank will blow the seals out. If I’m not mistaken, the transfer ports come into play ...more

No concern, if you looked at the leak down tester in the link provided you would see a pressure regulator so you're not applying high pressure. Obviously you have never done a leak down or you would understand that. Once pressure is applied to the top-end it will force the piston down provided nothing is holding the crank from turning. The piston will travel down to where it reaches the top of the transfer ports (provided the intake and exhaust are plugged), once it reaches the transfer ports the pressure will equalize between the top-end and the crankcase. At this point you can then check for leaks.

I've done leak downs on 2-strokes through the spark plug hole, the intake, and the exhaust. Just need to find the correct plugs. The object in all three have always been the same, check for leaks on crank seals, center cases, base gaskets, and head gaskets.

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2018 KX450F
2005 KX250
2003 KDX 220
1984 KX 80
1982 RM 80
1980 RM 80
1977 XR 75
1969 Honda Mini 50

10/30/2020 7:16 AM

No need to be condescending...

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