My Craftsman Model 358.797342 Leaf Blower would not start and I found that the headbolts had loosened causing the compression to be low. I tightened the bolts, the blower ran OK for a few minutes and suddenly quit. It had low compression again, but the head bolts were still tight.Compression is about 75 pounds. I had previously replaced the carburator, fuel line and filter. It has spark. Are there other things I should check for that might cause a sudden drop in compression?