Wodruff key

[cheapracer]

It's the taper that holds the flywheel on, the key is just to locate it wheres it supposed to be on the shaft. If it's coming loose you have taper problems not key problems. Those here who work in factories know that taper shafts (drills, lathes etc) just push in with your hand yet need a wedge and hammer to remove them again.

Sometimes hours of lapping is required to match the tapers again after damage has occured or idiots that put them on with rubbish on the shaft or flywheel.

Don't forget after lapping to remove the lip that you create on the fat end of the crank taper - this lip is often a source of trouble on a damaged/worn taper as people think the flywheel is tight but it's just butted up against that lip and still not secure on the taper.

[Mike52]

Don't forget after lapping to remove the lip that you create on the fat end of the crank taper

Is that possible ?
After all it is a taper and the flywheel keeps moving towards -----> the FAT end the more you lap it.

[cheapracer]

the flywheel keeps moving towards -----> the FAT end the more you lap it.

Hope so, that's where your new taper is created.

Yes it moves up the taper that's why you get the lip. A flat draw file and a few minutes will do the job. I have had to remove the lip first that's there from being loose then lap then remove the lip then lap then etc etc. as the lip also stops you lapping.

When I did my apprenticeship many bikes being serviced still had things called points and condensors requiring flywheel removal to change them! The good 'ol days - yeah right.

[chrisdespo]

We Know the taper holds the flywheel and the key locates in correct position but if the key and the tensions were corect in the first place the taper would not be worn or damaged, this is just an observation i make. i guess with old things you never know what the dill before you has done.

[pancho]

 The key does Nothing but locate the flywheel for timing. The minute the key takes load it means the taper has slipped.
pancho

[chrisdespo]

generally not tightened to the corect tension on a taper in good condition many a time i have seen a flywheel or rotor loose and damage key and once key has been replaced and tightened corectly you have no more problems untill a backyard mechanic has a go again and then when is stuffed again it would be brought back to the shop and fixed again properly not just keys here i am talking about engines and all other assorted components. and yes i know not all backyarders are bad mechanics just like all  not shop mechanics are good at what they do. I know some really great riders that can fix anything and then there are others that ride like angles and couldn't fix a tap washer.