These were known to be lean when new. Back in those days you would nurse it home lean from the showroom and pull the bowls to rejet. Gas has evolved since then too, reed vapor pressure has changed as has octane, and beneficial additives are virtually nonexistent these days.
I have done extensive experimentation with jetting and needles and slides over the years to get to where I am now. I hate to pull the carbs so I have figured out ways to do nearly everything with carbs in place. I did have to pull them off last year to replace the decell diaphragm finally, I just got tired of the backfires.