79yz400

Hey guys, Im new to this whole thing. A little over a year ago I picked up an older Yamaha 400, believe it's a YZ from what I've seen, though I am unsure of what year it is. To make a long story short I bought it off the guy for cheap, because it had a blown head gasket. I purchased the new head gasket, installed it properly according to a little bit of help I got from a motorcycle mechanic at the shop. I put some new fuel in it mixed with some nice synthetic 2 stroke oil. It took a while, but it ended up starting, very excited the first time I heard it run. However this was short lived, the bike was idling very high, so I adjusted one screw, believe it was the air screw, and brought the idle down. I than took it for a little ride. As I was riding it, I punched the throttle, but the bike didn't seem to go anywhere, just revved up?? I continued driving and all of sudden the throttle was stuck, in a panic I hit the kill switch....nothing. The bike was hitting its rev-limiter or something. So the first thing that came into my mind was clutch, and gear up, did this and dropped the clutch, stalling the bike. I was now officially afraid of the bike, it was the first time I've ever ridden a bike... I was a little disappointed but the guy did mention something about throttle sticking, so it wasn't something I didn't know, I just didn't think that it would happen right away. I than proceeded to pull the carb off, and try to possibly untwist the thottle cable. I than also (for some stupid reason) thought it would be a good idea to fool around with the screws on the carb. Now the bike doesn't start It's been about 6 months since I've touched it, not having or making much time for it. I think it needs new clutches, and new plugs, but I don't know how to tune the carb. Is there anybody out there that can tell me what to set the carb at, so that it will at least start?? or should I just bring the bike to a bike shop?? And is there anything I can do about that kill switch not working?? Thanks guys, hope someone can help me Brian