Leak down tester? (2 stroke)

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8/20/2018 12:45 PM

What all is needed to build one for cheap? And how exactly? Also will a bike pump work instead of an air compressor? I know you only put 5-6psi or you risk blowing bottom end seals.

How long ahould I wait as well? I saw one guy say wait an hour, some guys say 5-10 minutes. How many psi can I lose (if any) and be good?

What should I use to spray around the motor inside and out and not ruin anything?

I know it seems straight forward, but I have never had to do a leak down teat by myself before... so some advice as well would be great.

Thanks.

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8/20/2018 3:22 PM

You can use an expandable rubber freeze plug for the exhaust port and pvc pipe cap with an air chuck in it. You and use the spark plug hole for the air guage.
Pump up to about 6 psi with the engine at top dead center. It should hold for about 4 minutes with less that 10% lose.
That checks your head gasket and rings.

If that checks ok, then repeat at BDC to check reeds, cylinder gaskets and seals. ( It will leak off faster in this position.)

Paw Paw

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8/20/2018 3:26 PM

Paw Paw 271 wrote:

You can use an expandable rubber freeze plug for the exhaust port and pvc pipe cap with an air chuck in it. You and use the ...more

Ok. And for the gauge, what type would you recommend that would screw into the spark plug hole? The ones i seen in youtube videos have the gauge at the end of the pvc extension coming out of the reed cage boot. Also wouldnt the gauge hit the piston at tdc?

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8/20/2018 5:33 PM

You can use an adaptor for the spark plug hole. Or you can use and old spark plug with the guts removed and the either weld in or glue in the needed fitting for the guage.
You can use a water pressure guage.
There are so many different ways this can be done on the cheap and like you said there are many good videos on youtube to help.

Paw Paw

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8/20/2018 5:41 PM

Paw Paw 271 wrote:

You can use an adaptor for the spark plug hole. Or you can use and old spark plug with the guts removed and the either weld in ...more

Could i keep the plug in the head and use this? Found this setup via thumpertalk user a few years ago... also im assuming the gauge has the piece to hook the bike pump to? Sorry im new to this whole diy teater thing lol...
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8/21/2018 5:13 AM

That works too.

Paw Paw

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8/21/2018 11:57 AM
Edited Date/Time: 8/21/2018 11:58 AM

Alec138 wrote:

Could i keep the plug in the head and use this? Found this setup via thumpertalk user a few years ago... also im assuming the ...more

Me also curious about how to make a tester and new to it- thanks PawPaw for the info and also good questions Alec- as I also was wondering sort of the same. Good info and useful thread. smile

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Always was an excellent rider ...... at crashing usually

Moto Aspes, you know you want one

8/21/2018 6:21 PM

Paw Paw 271 wrote:

You can use an adaptor for the spark plug hole. Or you can use and old spark plug with the guts removed and the either weld in ...more

Alec138 wrote:

Could i keep the plug in the head and use this? Found this setup via thumpertalk user a few years ago... also im assuming the ...more

a22 wrote:

Me also curious about how to make a tester and new to it- thanks PawPaw for the info and also good questions Alec- as I also ...more

Easy to make with PVC fittings. Hardest thing to find is the guage that has the fitting for a bike pump to go on to and the threaded female side where you screw a threaded pvc adapter into.

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8/22/2018 12:04 PM

Alec138 wrote:

Easy to make with PVC fittings. Hardest thing to find is the guage that has the fitting for a bike pump to go on to and the ...more

I found that exact gauge at Home Depot. I think it was for natural gas lines.

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8/23/2018 8:10 AM

Paw Paw 271 wrote:

You can use an expandable rubber freeze plug for the exhaust port and pvc pipe cap with an air chuck in it. You and use the ...more

Rubber freez plugs do work well and come in an assortment of sizes.

However I disagree with it checking the rings on a 2 stroke. Rings have a small gap the ends (clearance listed in service manual) so air flows right past rings. The 2 stroke test checks the sealing of the complete department. Power valves can often have leaks.

A 4 stroke leak down test tests the leak % and can point you at rings, gaskets and valves for leaking.

As a professional MC mechanic I purchased mine from Matco. These are the 4 stroke leak down &compression gauge. I used the spark plug thread on the 2 strokes with a hand pump with low PSI gauge. I lent it to someone and well they kept it so no picture ermm

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9/8/2018 8:59 AM

Kids, kids, kids...

You are trying to make a mole hill into a mountian here!

First read this from Harry Klemm. http://www.klemmvintage.com/airleaks.htm

Then order this in. This is the basis for your tester.
https://www.ebay.com/itm/Gas-or-air-test-set-with-2-15-PSI-gauge-3-4-NPT-plated-steel-hex-body/162644850668

Easy Peasy baby!

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A big thanks goes out to Donnie at Morgantown Powersports and RJ at Beaver Creek Cycles