This lawnmower was working in that it started fine but I guess I never really put it to the test by mowing a complete lawn. Anyway yesterday I tried to fire it up and I found it hard-starting but it did fire up briefly and then it felt/sounded like backfire and I haven't been able to get it to start again. Spark is there, carby fine I measured the compression via a compression gauge and it reads zero. I have another Powertorque and it reads 90 psi. I know that compression gauges can't be relied on with these machines but have 2 questions.
1. What could have happened here, head gasket blown?
2. Does a compression gauge take into account crankcase compression? Could a bottom seal have gone and that stops it from firing up?

[Linked Image]