Post Master General
Join Date: Apr 2012
Location: Bowling Green, VA
I Ride: '09 ZX6R
In this respect a bike motor is no different than a car motor..... sailors who go on 6-8 month deployments leave their cars sitting for that period, go out and turn the key and drive away.
With the current design of cylinder walls, it's nearly impossible to have the oil film go away. Nikacil, and whatever the other mfgs call their surface treatments are almost like a diamond coating on the cylinder walls to keep the steel piston rings from wearing on the aluminum. It's a super fine grit bonded to the surface, and the rings ride on the tips of the granules. The grit is so fine, it really doesn't wear on the rings.
Because of the sides of all of those (millions?) granules, the oil has a ridiculously large amount of surface area to stick to. So much so, that gravity will never pull all of the oil off the cylinder wall. Same way that plain bearings on the crank, and cams will not run dry. Those first few seconds without oil pressure bringing in a new supply, it's best to not work the motor any harder than you need to -- once the supply is replenishing the oil between the bearing and the rotating part, all is good.
The gap between a bearing and a rotating part is extremely small.... if a cam sits still for a really long time, it will eventually push the oil out of the way, and make contact with the bearing. A circular part eventually concentrates all of the pressure into one point and that will touch the matching surface.
If there is any water at that point, and you have a steel part resting on a bronze bearing -- you have a battery, and galvanic corrosion will start. (This is why fresh oil before storage, is such a good idea. Reduces the amount of water available.) The lowest point where oil pools, you will find whatever water was circulating trapped there as well.
A bike in motion constantly sloshes everything around so it doesn't pool as much.....
Brake fluid draws water out of the air, and it's very similar to oil in that the water is more dense, and the water will sink to the lowest point, and cause corrosion.
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