Ethanol gas - same old story:
Three weeks ago, on my stock '76, I threw caution to the winds and got a tankful of Petro-Can hi-test gas, shown as up to 5% ethanol. Over the next week, I did about a hundred miles on it and then filled up with my favorite, Shell V-Power, no ethanol, did 30 miles and then parked it till this morning.
Hardly out of the drive, it gets an intermittent miss, which comes and goes for 10 miles or so till I get to my destination. Sits an hour, starts fine but the hesitation is bad enough and erratic enough that I start to fear for my appearance at the Vintage Yamaha Rally! Get back home to look it over and it stalls in the drive. Look it over nothing seems amiss, so down the road again.
I took the only curvy road in Kent county through Jeannettes Creek to Lighthouse Cove and came back the long way. This time, it ran perfect the whole 60 miles. I am guessing the the two week lay off allowed the gas to phase separate and to attract lots of moisture from the humid air and it took 20 miles to burn out or properly emulsify it again.
Moral of the story: Ride 'em, don't hide 'em.
Don't buy ethanol flavoured gas.