Thanks guys for your great input!

When I first got the motor I did infact check the crank runout against the prop hub face and found it 2 thou out. Not perfect but not bad either. The prop tracked within about 2mm from memory. There was no slop detected in the bearings in any direction but that was only from basic physical/visual checks and not disassembled and measured properly.

It's true that I didn't check the bolts as often as suggested above so this may end up being the cause. Ok, I need to order a new set of bolts as I borrowed the replacements from my 85. Is there a tensile strength I should look for? The M5 bolts I have here look like they have an 8.8 stamped on them.

Many thanks, Norm.