What a shame that happened. It was stuff like that, that got me started doing my own work back in the 60's .
Same here. My C200 developed a high speed miss, which got progressively worse over time. Nothing I did seemed to help, so I finally gave in and took it to the Honda shop in town. They said it needed to be bored and a new piston fitted, which was damn expensive on a paper route budget. When I picked the bike up, they said to take it easy for a while to break it in, so I did. After what I thought was enough time, I started riding it harder, pulling more revs, and the miss was still there.
The spark plug was blackish, so I took the carb apart for about the 100th time, and put it back on, leaving off the rubber tube that connected the back of the carb to the spigot in the frame that went to the air cleaner, since it was a pain to get in. I took the bike for a quick ride, and it revved to the moon without a hiccup!! I didn't know what I did this time that was different from the previous 99 times, but I was ready to ride after months, so I fit the air cleaner hose, strapped on my helmet, and jumped on the bike! My excitement lasted for about 50 yards, as the engine started missing as soon as I revved it in gear.
The problem was a plugged paper air filter all along.