Stephen
I have an 2007 FLSTC 96ci , I had same issue after fueling, it started to sputter 30 minutes after filling. Does the same thing as your wife’s FLSTC. I changed plugs, still the same. I cleaned air filter, still the same. I tried puter diagnose, CODE P0131 which is O2 front sensor, called Harley and asked ” if I disconnect the O2 front sensor, will it still run?” Harley said ” yes but it will throw code” . Once again disconnected the O2 front sensor( seems to me I should be able to remove too, people do run straight pipes on same motor!), did the same again, misfire. Charged the battery, same again, misfire. My last resort now is change the fuel, maybe this will work. [(I have 37,000 miles on my 2007 FLSTC,just read another blog that the Harley twin cam is manufactured with plastic pieces on the gears!! Harley does not recognize this
failure as factory recall. Only solution change to straight gear set up. ..but first I will change fuel. (Just a friendly heads up, as Harley does not recognize this failure as their own!)]