Dick says an answer is only as correct as the information given
Dick has some questions for you Micknmeld
Dick asks did the valves require re shimming when they were done
Dick asks was anything else anything at all done when the valves were adjusted
Dick asks did whoever did the valve job know what they were doing
THe valves where replaced by a Yamaha dealer
Dick asks what fuel does he use
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Dick asks what is the plugs colour when removed
Where a 4 stroke plug is covered with a dry, black carbon coating, it may be cold fouled. Dick says this can be caused by the wrong plug too cold excessive idling light loads carburetor choke out of adjustment defective spark plug wire carburettor adjusted too rich and low engine compression
this is cold fouling.
Dry black carbon, the spark plug cap had come away from the hi tension lead, I screwed it back in but you may be onto something there
Black damp carbon may include the wrong plug too cold again excessive idling carburettor adjustment set too rich this is Wet Fouling. A gray white blistered appearance or burned electrodes could be that engine may be overheating. Causes include plugged cooling fins, bent blocked cores carburettor set too lean this is a result of overheating
