True .. these motors will "run fine" with current "unleaded fuel"... However without the presents of lead in the fuel, leadoxide is not created when burned. This was what lubricated the (non-hardened) valves, seats, and guides..
Now, this information is being dug up out of my head so I can't be held responsible for its accuracy..
pre-70s autos (I have NO info on motorcycles) were built with motors requiring "lead" in fuel. I have heard stories of motors running for years into the future on unleaded gas. I was not as fortunate, my straight 6 burned somevalves.. requiring head work..
I had been told (late 80s) that unleaded fuels had additives to a assist with valve train lubricarion... but this was a little to late... these vehicles were driven daily from the 70s into the late 80s without any "leadoxide" unless it was added by the operator each time. Also these "additives" were not available to the "public" untill late 70s early 80s... Think about what it would do to a motor..
Believe it or not.. the "powers to be" are doing this again with ethenhol in fuel ( destroying[crushing] cars from the inside out). The American people fell for the "clunker buy back" program in the early 2000s.. because the big 3s auto sales were crashing.. People that bought new cars (origional owners) were "recycling" their cars by having new motors and transmissions installed at a fraction of the price of a new car. I read a study when pres clinton was asked about his old 67 mustang. It had to do with environmental pollutants and one point I read (not exactly sure of percentages)..,"During the life of a automobile, 90% of the pollutants from that car that enters the environment IS WHEN IT IS MANUFACTURED...
So when people were swapping out drivetrains, "recycling" their cars.. this percentage was eliminated already no with the purchase of a new car...
The "clunker buy back" cars were destroyed at the dealer level..Fluids drained and a solvent was added to the motor untill the engine seized... these vehicles were totally "crushed".. parts weren't "picked" or recycled... This caused a HUGE problem in the "after market parts business as "cores" (motors, trans, master cylinders, brake calipers etc.) that were normally used or obtained were destroyed..
"Ripple effect"..
Now, "hard parts" are surviving .. but ehtenhol in fuel is destroying "soft" parts.. (hoses, "O" rings, gaskets)... and with EPA, and computer systems (EVAP).. just swapping out a poertrain won't be cost effective as it was before..
DAMN... sorry, for the rant..
so, do some research, test the "health" of your motor (compression-leak down)... with a low mileage bike and today's additives.. you should be fine ..
I do find these motors tune and run better with non ethenhol fuels..
Just my $.02