I have a 2014 that started stumbling earlier this year after doing Beartooth Pass ride at High Altitude. Not bad gas. Has been in Honda Dealer ship twice for this issue ( still under warranty). 1st time new fuel pump, but did not fix the problem. second time (still there for last 3 weeks) even after bring in what they called "District Tech". They tried another fuel pump, now awaiting fuel pressure regulator. I'm planning on picking up the bike this Friday and ride it like with the stumble. What else can I do? Clearly Honda and techs don't have any idea what to do.
Stumble started at about 52k miles I have put 5k miles on bike with stumble. Stumble has not gotten worse.
The stumble is slight when I roll on the throttle lightly/normally when shifting from 1st to 2nd, 2nd to 3rd, etc. a flat spot at about 1700 to 2000 RPM. Hot or cold make no difference.
Reading many other articles, I cannot find a definitive problem and solution.
Honda dealer says valve adj overdue and want to try that - over $700 maint item. If they would guarantee this would fix it, I would pay the $$, however, I doubt seriously this has anything to do with the problem.