I dismantled a few 100cc engines in the 80s, including a Manx. In all cases the crank was a sliding fit in the bearings, usually a v. loose sliding fit!!! ie the crank journals were worn. I bought a brand new TKM BT 82 and had to make a puller to separate the crankcases. So I am assuming that new 100cc engines were built with an interference fit between crank and bearing , and bearing and housing, and the crank to bearing fit became loose in use. Hard to think that a 40 + year old engine will not have some wear at the crank, could the bearings be rusted on.Heat on the scrap bearings should help if there is rust, then you need either a proper bearing puller or improvisation (two flat bladed screwdrivers tapped in?) to get the bearings off.
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