Leak down test procedure (CFI-2 motor) question?

Murph

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www.missingdigitmotors.com

• Sep 24, 2012

• #1

2XM3 said:

...http://www.summitracing.com/search/...s/?keyword=leakdown+tester&kr=leakdown+tester

Warm up motor, pull plugs, set piston at the exact top of its stroke, hook guage up to air, zero it, hook to cylinder...read leakage done deal.

Click to expand...

I have done tons of leak downs on 4 stroke motors....never a 2 stroke.

Listening with a grain of salt.....a dealer mechanic told me I had to pull motor and seal intake and exhaust for "proper" leak down test.

Hoping this isn't the case, 2XM3's procedure sounds a lot better to me!

What is the proper procedure on these motors?

 

AKSNOWRIDER

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• Sep 24, 2012

• #2

2x's procedure will work fine, but you need to hold the crank from turning or when you hit it with air it will roll the piston down and uncover the ports...

 

O

ottawaair

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• Sep 24, 2012

• #3

To perform a leak down correctly, the ports need to be blocked. This way you can check the entire motor for leakage ( crank seals ). By holding the piston at TDC, you are only checking the rings for blowby. Which a compression test will tell you. I used to do leak down, then vacuum tests on 2 strokes, just to verify crank seal condition.

 

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01ZRTCAT

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• Sep 24, 2012

• #4

So how would one go about sealing both intake and exhaust ports?

 

tundramonkey

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• Sep 24, 2012

• #5

Seal the exhaust side at the end of the y-pipe. Seal the intake at the intake boots. (Just before the reeds) Doing it like this will allow you to check for intake leaks and the pistons don't have to be covering the ports.

Sent from my DROID BIONIC using Tapatalk 2

 

PaulAnd

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• Sep 24, 2012

• #6

I understand doing a cyl. Leak down test on a 4 stroke, but why a 2 stroke? If there is good and even compression is there a need? Sealing off the intake and exhaust ports are needed for a vacuum test, I like using an automotive evap smoke machine to test with very slight pressure.. and the built in gauge on tester will confirm no leaks. Smoke helps find the leak if there is 1. Check the manual for the correct port on the case to use. I think the dealer tech might have confused cylinder leak down test and case/seal leak test

 

Rick!

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• Sep 24, 2012

• #7

PaulAnd said:

I understand doing a cyl. Leak down test on a 4 stroke, but why a 2 stroke? If there is good and even compression is there a need? Sealing off the intake and exhaust ports are needed for a vacuum test, I like using an automotive evap smoke machine to test with very slight pressure.. and the built in gauge on tester will confirm no leaks. Smoke helps find the leak if there is 1. Check the manual for the correct port on the case to use. I think the dealer tech might have confused cylinder leak down test and case/seal leak test

Click to expand...

For the same reasons - leakage beyond 5-6% is a performance loss. Your comp gauge won't tell you that. Back in the old days, before evap smoke machines, a lit Marlboro or True Menthol, and a piece of rubber tubing told me whether the leak was intake, exhaust or blowby.