Outdoor Power Equipment and Small Engines - compression test - advice

I ran a compression test on a tecumseh motor. The reading was around 40psi. I poured some oil in the cylinder and tested again getting the same reading. Now everything I have read about doing a compression test points to a problem with the head gasket and not the valves or rings. I took the side plate off and watched the valves go up and down. Is there another test, other than a leak down, I can do to pinpoint the problem area before I take the head off. How accurate is the compression test from a trouleshooting perspective as it is described in most manuals. How can you really tell if it it the rings, valves, or head gasket from a test.

If your engine has compression release it could read 40 PSI and not have any problems. Since you had no change in compression you would think a leaking valve or head gasket could be the source of lost compression. The only sure way of knowing combustion chamber integrity is a leakdown test. With the leakdown test you can determine exact source of compression loss and if it is acceptable.

Harbor Freight sells an inexpensive leakdown tester. - Harbor Freight Tools - Quality Tools at the Lowest Prices (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94190)

If this is not an option for you, ask a local shop what they will charge to perform the test.