I'm a follower of Super Hunky (Rick Siemens) on this. I lube the wristpin bearing, but not the rings or cylinder wall. As soon as the bike turns over, it is drawing premix in, and it gets lubed that way. I think oiling the rings and/or the piston or bore just sticks the rings, and there is no downside to assembling dry. I know some will say the bike needs lubrication until it fires, but as I said above, as soon as the induction charge is drawn into the cylinder, the premix contains all the lubrication the bike needs.
there,s a down side on installing dry imho
all the movement done for check of piston travel and fitment ,
without adding premix to piston and bore.
will cause small sand/dustparticols (if there)to leave their marks on the bore and piston.
oil makes them less harmfull ,because they get weak and will be tranported down by the oil too.
i like a good amount of premix on everything that needs it ,then i let the piston travel a while ,
with moving the kickstarter by hand ,and if its found to be good i stick plug and start it up .
also bare metal on metal itselfs is not what you should want i believe