Re: Infernal Machine - Help
Crassius covered much of what you need to check but I'll ask a couple of questions.
What fuel to oil ratio are you using? We've found that the recommended 16:1 is too much oil. You can safely run 24:1 or better yet, 32:1. The high oil content can be a cause of exhaust clogging.
How does the spark plug look? Dry or wet and oily? What color is the porcelain at the tip? And how are the electrodes and what plug gap are you using?
Have you checked the air filter? They need periodic cleaning.
If the rings and cylinder wall looks good, no gouges or scrapes, then I would be suspicious of the head gasket. The fasteners are notorious for loosening and allowing compression loss. We always suggect replacing the chrome acorn nuts with hex nuts. The acorns can bottom out and keep the cylinder head from seating well against the cylinder and gasket.
Let us know if any of our suggestions help.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"