Small Engines (Lawn Mowers, etc.): Old Lawnboy Engine, wd 40, cutting blade

Question
I have an older lawnboy push mower, with the 2-cycle engine. I had been mowing for a couple of hours and just as I was about to finsih the engine died. At first the motor was locked up, but I pulled the plug wire and was able to turn the motor over with the cutting blade.  I then tried to start it but noticed I had no compression at all, the engine just free wheeled.  I wasn't using the Lawnboy oil to mix in the petro, but I have on occassion did not use their oil with no problems. This motor was a short block that I purchased probably 30 years ago. I purchased the lawnmower in 1969 or mabey in 1970, not sure.  What do I do to check this engine out?  What procedures do I take in doing so? I also replaced the deck, as the old one had cracked and broken off.

Answer
With the spark plug removed, insert a WD-40 or drinking straw in the spark plug hole.  Turn the engine by hand and see if you can feel the piston pushing on the straw.

How much is the mower/engine worth to you?  It could be expensive to repair but if you really like the mower it may be worth it.

Let me know if the piston pushes on the straw.

Eric