FROM Web Bike World
*WD-40 & Motorcycle Chains*
Some interesting information on the use of WD-40 on motorcycle chains:
"Saw your article on using WD-40 for chains and you asked for evidence of potential harm that WD-40 can do, so am attaching a photo. This photo is of a bearing surface from an airplane.
This is a ball and races in a sealed bearing that had been subjected to regular use of WD-40 for a year or two (see attached photo below). The grease was NOT cleaned out before taking this photo - there simply is no grease and the brownish tint is really rust.
The ball had grooves (visible) and was shaped like a potato chip. The races had not evenly worn (see sectioned edge) and were rutted in spots, although neither shows too well.
We learned that WD-40 is really good for the light uses that it was intended for and that needs to be emphasized. However, it is largely a penetrant, which will do just that!
Once it penetrates into the sealed area, it dissolves the petroleum out of the grease, leaving the clay binders. What's left in the bearing is essentially dirt that cakes up, causing the balls to skid. Without the petroleum, the bearing will also rust.
The reason that kerosene and diesel fuel are still favorites and recommended by the chain people is that while both can be penetrants, they are a thicker petroleum and just what the O-rings are trying to seal against. Of course, gasoline cleans about the same, but with thinner viscosity and better penetrating power. In all honesty, I still use gas to clean (I'm lazy), but don't beat the bike often, regularly measure for linkage stretch and sprocket wear, and re-lube on every other tank of gas."
Moral of the story is to not use WD-40 for cleaning motorcycle chains.
