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ash fouling


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I could imagine coolant in one or maybe two but not all cylinders. Besides, I hear no mention of coolant loss or overheating, and nothing about steamy exhaust. It's hard for water with a few pounds of pressure to force it's way into a cylinder with 150+ PSI of compression pushing back and even more when firing. Usually the compression enters the cooling system and over pressurizes the rad cap and coolant is forced out.


I've seen lots of exhaust valves white (or at least very light) in color and it's normal. 



Before putting a wrench to it, post some pictures of the plugs. Could be just the oil from bad valve seals.... not bad enough to blacken the combustion chamber but slowly over time. The plug cleans itself of carbon but the 'ash' in the oil crusts on.

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Generally hotter exhaust valves tend to be white-ish in color while the cooler intakes are black or very dark. A dark exhaust valve might mean something is wrong in that cylinder and thwe valve isn't as hot as it should be... for whatever reason.


Coolant entering a hot combustion chamber will steam clean everything. I changed a h/g on my 620 and the piston top looked like new out of the box. The combustion chamber as well but there were some crusty thick carbon deposits that flaked off to the touch.

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