I was just wondering if its ok to use wd-40 to clean my engine? I sprayed some on a cloth and it seem to to clear up a spot on the motor that was dingy. I sprayed a little on the front part of the exhuast pipe to remove some rust. It took off the rust real good, but I had started the bike and it started to smoke where I put the wd-40 on the exhuast pipe, is that normal?