Nearly a month ago, we looked at the problems created by crankcase ventilation. These ventilation systems route the combination of gasses escaping past the piston rings, mixed with vaporized engine oil from the crankcase, to the intake tract, where they are supposed to be burned on a second trip through the combustion chambers.
Although Positive Crankcase Ventilation (PCV) systems have been required since 1961, they have serious drawbacks – mainly the accumulation of carbonized oil on the walls of the intake and exhaust passages, the backsides of the valves and in the combustion chambers, where it badly reduces airflow and can cause overheating. In addition, oil particles in the combustion chambers can initiate detonation, quickly creating major damage. Let’s look at what you can do to avoid such problems on your own motorcycle engines.
It has been reported that, at idle, typical blow-by composition is 67 percent oil, 22 percent fuel, 10 percent water and 1 percent solids by weight. An inevitable by-product of combustion, water is the greatest single cause of preventable engine wear, creating corrosion by oxidation and acid formation. Tests have shown 0.2 percent water in the engine oil is typical but levels of .4 to .5 percent are not uncommon, and at these higher concentrations, free water is likely to separate out as the engine cools. Plus, ironically, the situation is made worse by the water dispersal additives in modern engine oils, and the use of E10, E20 or E85 fuels (containing 10, 20 and 85% ethanol) that both attract water and are more electrically conductive than gasoline, creating galvanic corrosion.