Motorcycle Repair: Bottom end rebuilding, stroke oil, motor oil

Question
What is used to lubricate the main crankshaft seals during assembly. Especially the left (or flywheel) side.
Thanks.

Answer
Bill,
 No big concern here.  A bit of 2-stroke oil or even typical motor oil will do you fine.  They are continually lubricated by the pre-mix entering the crank chamber.  Apply "Three-bond" non-hardening sealant to the case flanges, NO silicone.

Mike