Well the sled there, it has a fresh engine in it. I just rebuilt it all. Got her runnin... and It ran great for a few minutes. It idled kinda high but I wasnt concerned. I then took it out and rode it pretty easy, ran good for about a minute, then I gave it a bunch of gas to try and clean it out. It was getting pretty loaded up. I think I ran it up to about 6 or 7 grand then it started backfiring. Now it wont idle on its own. Constantly backires. Was even throwing a flame out the tail pipe. And is a bear to start. It ran awesome for about a few minutes, then all of a sudden it did this. The engine isnt making any abnormal sounds. Im at a complete loss. Please help me. Thank you.

sounds like a fouled plug to me and did you mix extra oil with the 1st tank of fuel you can burn a piston if you don't mix it that way. Jerry

Well the sled there, it has a fresh engine in it. I just rebuilt it all. Got her runnin... and It ran great for a few minutes. It idled kinda high but I wasnt concerned. I then took it out and rode it pretty easy, ran good for about a minute, then I gave it a bunch of gas to try and clean it out. It was getting pretty loaded up. I think I ran it up to about 6 or 7 grand then it started backfiring. Now it wont idle on its own. Constantly backires. Was even throwing a flame out the tail pipe. And is a bear to start. It ran awesome for about a few minutes, then all of a sudden it did this. The engine isnt making any abnormal sounds. Im at a complete loss. Please help me. Thank you.

Check your Crank seal those buggers will quit on you anytime. new or old if not check your vacuum hose for ice, plugged or a hole. thanks Mr sir lol.

also check to make sure a choke or float isn't stuck and the bottomend or exhaust got flooded with gas.
you said it idle high for a bit,check to make sure you tightened the carb boots and that they arn't cracked.

All good things to check. Don't forget to eliminate the possibility of a ruptured fuel pump diaphram also. If you check out most of the threads in this forum related to runability issues, you will find a lot of suggestions and great advice on possible causes and things to try and/or do to pin down your problem.

Most of these two stroke engines use a waste-spark type of ignition, which means that when any spark plug fires they all fire. So if your engine is backfiring and shooting flame, chances are real good that the exhaust side of the engine is flooded with unburnt fuel. That can be caused by a number of different things, so try to eliminate as many as you can and you'll find the problem.

Keep us up to date.