Posted by Max on June 15, 2003 at 04:43:27:
In Reply to: carbon buildup on vacuum piston posted by Richard fssnoc#(Ks) on June 14, 2003 at 20:19:27:
Been thinking over your concerns and even though the air is continually moving into the engine, it is being pulsed by the rapidly opening and closing of the intake valve. The crankcase vapors will work to attach themselves to the equivalent parts in your automotive engine, throttle plates, carb body and intake manifold..Thats why they recommend a tbrottle body cleaning on some vehicles. The air bypass ports controlled by the computer plug with the sludge and prevent correct operation. I recommend loking at 2 things, 1) engine blow-by, the parts of the air/fuel mixture and combustion gasses that get by the rings and into the ventilation system and then are allowed to recycle in the intake. Best tested wuth a cylinder leakage tester, unless a compresion test shows up very low and in the ring sealing. and 2) intake valve adjustment. A valve that is too tight (low) on the adjustment valve will be open longer and allow more compression gases back in the intake runner. Run them in the middle of the specification. Loose is not good as it reduces power less fuel and air in and allows the end of the valve stem to get mushroomed.
Additives in the fuel could also be part of it, but I would think other cycles would be having the same kind of problems and the word would be out to the techs and other riders about fuel concerns and solutions (better brands).
Do both of you ride in an area that uses oxygenated (enathol alcohol added) fuel at this time of the year. It has a history of concerns hotly debated when introduced. One of which was how it reacted to metals in the engine systems. If so fueling in an area that doesn't have the additive might be a solution. I'll keep thinking on it.