Measuring Compression

krnuttleFebruary 13, 2014

I have an older JD Lawn tractor LT-155. I would like to get a measure of the remaining engine life and would like to check the compression on the cylinder.

What is the best way to do this?

Tips and recomendations?

PS Since I used to do my own service on my cars I have a compression gauge.

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If it has a compression release you'll have to rig a socket on a cordless drill using the flywheel nut to rotate it backward to get a true comp. test. Do one test then squirt approx. a tablespoon of engine oil in the cyl and do another test. A large increase in pressure indicates the rings are worn. How much life is left is a WAG depending on care and maintenance.

    Bookmark   February 13, 2014 at 1:55PM
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Do you know what the compression should be on the JD LT-155 with the 15.5 Kohler engine. The tractor was purchased new in Aug 2000

    Bookmark   February 13, 2014 at 4:52PM
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I think you are trying to perform an exercise in futility-
The manf's don't even give compression specs, but tell you to do a leak down test.
Even then, they don't tell you how much air should be leaking past at a specified pressure. It just basically determines where it is leaking.
Even if you know what the factory compression is, what rate does it decrease? What's good or not?
Also, when the engine is running, it won't leak as much as a relatively slow cranking engine.
If it isn't burning oil...........

    Bookmark   February 14, 2014 at 4:50PM
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OK I don't think it is burning oil, so I guess I should not worry about it.

I just found a coupon for 15% of the JD service kit for the LT-155, so I guess it is time to do the spring service. At $34 dollars for the kit I can not beat that price at the big box stores for the same price.

    Bookmark   February 14, 2014 at 9:09PM
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I would do compression check just to know a base line. Probably won't be much over 100 with compression release. I would think 80 or above would be good... I have 24 year old 14 hp Briggs vanguard that has 160 in each cylinder. It has held that for the 16 years that I have owned it. Also have Replacement 17 hp Kolher on my LX266 that's 100 with less than 60 hours on it. I did when it was new to know Base line.

As you said wouldn't worry about it if it runs good and don't puff blue smoke.

    Bookmark   February 17, 2014 at 7:54PM
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