Are you using studs or stock bolts or something else? I had this problem when I first built my engine using side cover studs from Burris. Initially I torqued them to stock specs that I cannot remember right now. Shortly into my first ride and I noticed a trail of oil behind me. The cover was loose and the gasket had shredded. It's the same thing as the head studs, I had to torque them a bit more for proper stretch. Dunno why I didn't initially think of this for the side cover, but I didn't. Also, on the second go-around I used a genuine Honda gasket that somehow fit my Predator Hemi correctly. It has not been a problem since. If you are using stock bolts, toss that junk. They apparently hit their elastic limit when installed in the factory. Perhaps they are torque-to-yield fasteners and no one told us?