1983 YTM200K Carb problems! help!

[TriMoto200_1983]

hello my name is nick. I have a 1983 YTM200K which i have bought about 2 months ago. The bike is in mint condition, the only thing wrong with it is, it idles way too fast. When i first start the engine, it will idle perfect. I keep the bike in neutral, and give it a few shots of gas, a little more each time, and when i give it a shot of gas just past half throttle, the bike will start to rev really high, not at a constant revv, but higher and higher every second, so i have to turn the bike off. I had the carburetor taken aprt a million times, and cleaned it out. But its still the same thing. Ive bought an owners manual off of ebay which shows the air screw adjustments which is 2 1/4 turns out. +or- 1/2 a turn. ive tried it all but it still happens....i have no idea what the problem could be. ive tried looking for a cab on ebay but theres absolutely no carbs on there to fit, but a million for the honda atc's.... i dont know why, but anyways.... the only place i can find a carb is on www.bikebandit.com. i can get a OEM carb for 286 bucks, or an aftermaket one which is about 70 bucks....the only thing is, the pic of the aftermarket one looks nothing like the original except the intake and outake holes. 22mm and 49mm.....anybody know if they would work....heres a link to the website......http://www.bikebandit.com/product/16986?m=8791&t=1

if someone could help me i would greatly appreciate it.... if you know someone who has a carb for sale please let me know! thanks....