I don't know what kind of motor you have, but I know that DA doesn't want the user dissassembling their motors at all. If you have a DA, just send it in for "freshening" in the off-season and they'll take care of you... probably won't even charge you. Good guys.

Other motors... call the distributor or manufacturer and talk to them about warranty policies before turning wrenches on the motor (other than the obvious... making sure your head is tight, etc...).