This brings to mind an episode many years ago when I used to be involved with repairing Husqvarna, Stihl and Sachs/Dolmar chain saws. One of my colleagues checked and adjusted the contact breaker points on a small Stihl. He had quite a battle to remove the flywheel from the tapered mount on the crankshaft. So, unbeknown to me, he coated the taper on the crankshaft with grease before re-fitting the flywheel. This came to light the day after the owner got his saw back - the flywheel had shifted on the taper, shearing the woodruff key in the process, and of course throwing the ignition timing out. When I questioned my co-worker’s decision to grease the taper, his reasoning was that since he’d had difficulty removing the flywheel, he wanted to make it easier ‘the next time.’
I recall reading somewhere that there should not be so much as a fingerprint on the taper, never mind a dollop of grease!