Boring Motorcycle Cylinders

Question:

I recently had motorcycle cylinders powder coated, and, unfortunately, some overspray entered the cylinders. I am not planning to bore the cylinders, so I was wondering if there is a method or product you could recommend to remove the coating from only the inside of the cylinders. Thanks. G. F.

Answer:

Being a former “shade tree mechanic” and engine builder, I can relate to your problem. My first recommendation is that you hone the cylinder walls to replace the cross-hatching groves that hold the oil on the cylinder walls. This is not as radical as boring and is necessary for a good engine rebuild. But most importantly, it will remove all the oversprayed powder from the inside of the cylinder walls. If you already honed the walls before sending it to the powder coater, then re-honing them may cause problems with your piston ring end-gap. As the cylinder walls are ground by the honing stones, the ID will increase slightly. This will mean your piston rings will expand the same amount, resulting in a slightly larger space where the ring ends meet (ring end-gap). As this dimension grows, the crankcase oil will be pulled into the cylinder causing an oil-burning problem with the engine. Your choice at that point will be to buy over-sized rings and grind the ends until the desired end-gap is achieved.

An alternate method is to remove the overspray powder using a strong paint stripper carefully applied to the cylinder interior. Follow the directions carefully to avoid any problems and always follow all safety and disposal recommendations listed on the paint stripper can.