Re: coking??
Coking is a white waxy like substance build up, A thick build up which is unlike any carbon build up one would ever see. Coking can reach a thickness of 1" easily in a rather short span of time.<br /><br />The only cause of coking that I have ever come across was that a engine would be over pitched. This results in having the carburetor butterflies wide open at full throttle, the spark advance set to full, but the engine would be unable to reach the proper rpms. This in turn prevents the engine from breathing properly, the exhaust can not escape normally, with the final result being.... coking.<br /><br />Your spark plugs should be Champion QL77JC4 plugs, gapped at .040 . Compression should be 100+ psi and even on all cylinders. Spark, w/plugs removed should jump a 7/16" gap with a strong wide blue lightning like flame.... a real SNAP!<br /><br />Soot indicates a weak spark. Check the continuity of the coil(s)... plug terminal to ground wire, plug terminal to primary wire. You should obtain a reading on both.