Try to start with starter spray (available in auto part stores). If it starts with spray, then you should check the carb (most likely) and fuel supply (less likely). My bet in your case is the carb, probably the primer bulb doesn't inject enough fuel for starting. You would need to take off and clean the carb, and make sure all passages (particularly priming) are unobstructed. If it doesn't start with spray, than either the spark is missing or weak (take the plug out of the cylinder so you can see the spark), or there is no compression (to check this, you need compression tester). Both of these possibilities are equally likely. I've seen an old mower where the exaust valve slowly sank into its seat after 10 years of work and decreased the valve gap from 0.006" (factory spec) to 0, leaving the valve always open. To fix that, I had to open the crankcase and shorten (file off) the valve stem by 0.006". Good luck.
Milan
July 2009
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