86 TR200 (ATC 200x) misfire at high rpm

[boy&hisdogs]

Exactly what the title says. I have an 86 Honda TR200 Fatcat. While riding, it misfires, sputters and dies when revved past about half throttle. While in neutral I can rev it all I want, but it backfires like crazy above half throttle. The exhaust is perfectly clear and colorless if it matters.

When I got it, it had been sitting in a friend's barn for a few years. I rode it everyday to work for a while, then bought my truck and pretty much forgot about the bike. Now it's been sitting for about a year, and she deserves better. I have decided to restore her to her former glory, but I need help as this is the first time doing real work on a motorcycle.

I replaced the spark plug and air filter, as both needed to be and I thought that this were causing it, but not so. The old plug was coated black and had a little gunk on it but I just figured that the bad air filter was causing it to run rich. Now I think the carb may dirty and be partially clogged because the bike had been sitting so long. It would make sense why its running okay when given only a little gas, but when more is demanded, it can't keep up.

What else could be causing this? What are some more clues I should look for to point me one way or another? Tests to be done, things I can check? I appreciate any input and please correct me if I am wrong about anything because I am very inexperienced and want to learn as much as possible.

[ps2fixer]

If it ran fine, then sat for a while, then acted up, I would target the carb. Fresh gas wouldn't hurt either since today's gas only stays "good" for something like 3 months.

[M.Pargiello]

Carb needs to be cleaned more than likely

[suzukiboy98]

my 200s had the same problem and all that was wrong was it had the wrong spark plug.

[yaegerb]

A few things to check:
1. Correct sparkplug and gap
2. Ignition Timing is correct
3. Main jet is correct
4. Ensure a strong ignition coil, CDI Unit or pulser generator
5. Ensure there are no obstructions in the fuel line or shut off valve
6. Ensure the ignition advancer unit is correct
7. Ensure that the fuel cap vent or fuel filter isn't clogged

Ensure all of those are correct and let us know what you find.