You need to check on a level surface. I prefer to check cold before start up. Too much oil is just as bad as too little. If the oil level is high enough for the crank to strike the surface, it robs engine power by forcing the crank through a heavy fluid, AND the oil gets aerated by the crank. Air in the oil is the kiss of death to your rod and main bearings, so overfilling is NOT good.
I had a discussion with Ray Plumb some years ago about the factory Honda CBR600 they were racing at Laguna Seca. He told me they picked up an extra 5 hp just by running the oil level half a quart low. Overfilling is undoubtedly bad.
Whether you need to suck some out is up to you. Be absolutely certain the crankcase is overfilled before you do this. The easiest way to change the oil level is to get the engine hot, then use a semi-rigid plastic tube that fits down the dipstick tube and suck out the excess with something like a 60cc veterinary syringe or some other vacuum source. If there's interest, I'll write up something about doing it. Otherwise, I'll leave it to the student to determine how best to apply vacuum and reduce the oil volume in the crankcase.
