We had this same issue year before last. Tried the plugs and no joy, turns out it was the coil. Sourced one out up here (Canada) and WOW! $$$.$$, so Google is your friend, and Dad found one in the States, Genuine Honda OEM at 1/3 the price up here but,,, he would not ship to Canada. So he had it shipped to a friends place in Arizona, whom he was going visit shortly thereafter, and then brought it home from there. It is staggering to see the markup on some (a lot) of the items up here in Canada. Some way some how, somebody didn't get the memo that our goods up here in Canada are not all delivered by bush plane or dogsled, and the internet makes the world a lot smaller. In this case, the amount that Dad saved on this coil, paid for almost all of his plane ticket down there and back, in my opinion that is ridiculous.
BTW installed the new coil, and that kicker has not run that good in years. I don't think that the starter even made one full revolution and the motor fired right up and runs perfect!
FH