Well let me tell ya…
YES!, by all means lap that sucker, here is why..
The taper of the crankshaft and the taper of the flywheel are BOTH made to be the same, BUT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
IF they are not within a certain amount of error, when you tighten down the flywheel one has to give and it will be the flywheel..Wanna see proof???
Here is it, the flywheel will split, and it should split right along the key way as that is the weakest point of the taper as the key is cut with what could best be called square corners which from a machining standpoint is the weakest.
Now what happens is they need only be off about maybe 1/2 a degree or less for this to be an issue, lapping the two removes that issue and literally matches the 2 tapers to create and much stronger attachment and ensures you don’t have any issues..
That being said the practice "SHOULD" be performed when using any flywheel that did not originally come from that crank shaft, and ESPECIALLY if you have had either the crank or flywheel hub machined. And to lap the two, you want a minimum of 75% contact on the lapped surfaces to consider it being within specs. 100% match is always best but 75% is considered good enough.
30 + years ago I joined the US Navy, and that specific process was taught to me…. from the picture you see above, you would think I would have remembered… well I did, AFTER I cracked this flywheel…
Good luck and lap that sucker…LOL
Regards
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