This happened to my pocketbike. First thing I must tell you... NEVER RUN STRAIGHT GAS IN A 2 STROKE ENGINE!!! Take it from a guy who's been there. 2 strokes need the oil in thre gas mix so tht it can lube up all the moving parts. Straight gas will just cause the piston and the cylinder to scuff up and it will make it hard to turn over, then the engine will start dying on you, then it won't start, then bam its seized... All this in under 10 mins... I did tht to mine but I was able to salvage it and make it work correctly In the end...
Ok now tht that's out of the way, take off your carb and unhook your throttle line etc from it. Then put the carb in some pure 100% lemon juice and boil it in tht for about 30 minutes. Then just let it sit in tht mix after its done boiling for about a day. Then take it out and let it dry a little in front of a fan or something, when its dry give it a good spray with some carb cleaner. Then just put it back together, mount it on your engine, put in some proper mix, and give it a few pulls. It should start, if not then give it a lil help with some engine starting fluid thru the carb. I had to do this twice before it started fine on its own...$
You may also have to adjust the idle speed screw when youy do this. So after you have the engine assembled and running screw it in all the way, put the bike on a standd an start it, itlkl be revving pretty high so the back wheel should b e moving cause the clutch is engaged. Turn it off, back out the screw a little, and start it again... Jkeeep doing this until the engine can start and idle at a good speed, and the clutch isn't engaged. It should sound like its ideling right also. When that's done rev it uop a lil and make sure tht when u release the throttle, it goes back to tht same steady idle, and you'll be allset...
Best of luck, hope this helps