I have a 24 year old (I think) Craftsman riding lawnmower with 12HP OHV Tecumseh OVM120-200017A engine aka 143.376012. I have always been able to fix it but not this time so far. It died just as I was driving it into the car port. I checked the spark, since I had a coil go bad once, but it has spark. I tried starting spray but no help. I did a compression test and there is no compression, however I think it might have a compression release mechanism for starting, not sure. I took off the valve cover an the pushrods, rockers and valves seem to be operating properly. The intake valve gap is .011" and the exhaust is about .130". That is huge, but again I am thinking maybe it is the compression release mechanism.

On the exploded diagram, the camshaft is #25 and in the parts list it says:

35314A Camshaft Assy. (Mech Compression Release)

Does the compression release work by changing the valve timing or by holding the exhaust valve open? I did read on the web one person said their valve seat popped out of the head. I stuck a borescope through the spark plug hole, with a right angle mirror, and the exhaust valve does seem to look "different". But I don't know enough to innterpret what I see.

Does anyone have experience with these?

Thanks

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra