Runs fine for 15 min then misses. Limps home and then hard to start. I though it was plugs, and when replaced repeated. Used old plugs on my other machine and they worked. so not case. The next day after charging the battery it started again no problem.. I will check compression today what is normal? I suspect maybe a head gasket leak fouling the plugs temporarily then drying out..Is this even a possible theory? I guess Compression test will help diagnose?