 Source of low compression |
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| 1bad914 |
 Jul 17 2006, 09:33 AM
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#1
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Senior Member  Group: Members Posts: 618 Joined: 6-May 04 From: Battle Creek, MI Member No.: 2,028  |
Is there anyway to truly tell the source of low compression in a specific cylinder, is it valve or rings, how can you tell?
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| Bleyseng |
Jul 17 2006, 09:48 AM
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#2
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Aircooled Baby! Group: Members Posts: 13,034 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
run a compression test on all cylinders...plugs pulled, throttle wide open etc.
note numbers then add alittle oil into cylinders, re-run test and note numbers. if it goes up alot then its rings as the extra oil will seal the rings. if its the same its valves |
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| 1bad914 |
Jul 17 2006, 10:04 AM
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#3
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Senior Member Group: Members Posts: 618 Joined: 6-May 04 From: Battle Creek, MI Member No.: 2,028 |
Dooohhhh! I knew that, I hate it when your memory lets you down, I guess I killed to many brain cells in my youth! (IMG:style_emoticons/default/drunk.gif) Thanks for the kick to my memory ! (IMG:style_emoticons/default/alfred.gif) (IMG:style_emoticons/default/biggrin.gif)
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| Dave_Darling |
Jul 17 2006, 10:57 AM
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#4
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914 Idiot Group: Members Posts: 14,990 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California 
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There is a little debate on how accurate this is for engines with a horizontal layout. (It doesn't seem to work well for some people?) A leak-down test will tell you about individual valves, and about how the rings seal at TDC.
...It's another option, at least! --DD |
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| Bleyseng |
Jul 17 2006, 11:16 AM
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#5
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Aircooled Baby! Group: Members Posts: 13,034 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
It just a way to get a read on the situation.
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| DNHunt |
Jul 17 2006, 12:01 PM
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#6
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914 Wizard? No way. I got too much to learn. Group: Members Posts: 4,099 Joined: 21-April 03 From: Gig Harbor, WA Member No.: 598 |
Get a leakdown test if you can. By listening for where the air hisses you can get a good idea where the problem is. In my case using a vacuum hose down the oil filler pointed to air leaking past the rings. You can listen down the intake for air leaking past the intake valve and up the exhaust for the exhaust valve. I suppose you might be able to hear a leak at the head too but, I don't know that for sure. It's really kind of a fun test.
Dave |
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