If you use WD40 to clean it, be sure to remove all the WD40 and replace it with a good oil. WD40 is NOT a lubricant, it is a water displacement fluid. If you use just WD40, it displaces the rust and leaves a nice abrasive bunch of goop in the engine which will do a nice job of wearing out the bearing at a faster than normal rate and scour the sleeve and piston. IMHO you are better off to NEVER get WD40 inside an engine.