trx400ex 07 not running properly HELP

A 2007 with a 2001 motor? Do you know the history of the quad? Check the air filter and see if it needs cleaning. Check the spark plug and clean or replace if needed. Whenever I have bought used machines in the past, I have always changed all of the fluids. This includes draining and flushing the fuel tank and if it had a carburetor, I would rebuild it. Try the preceding first because it is really easy to do. If this doesn't solve your problem, then you will want to check your compression. I do not believe the 01 has electric start. Is it really easy to kick over, or does it feel really loose? Let us know how it goes.

You are new to this but you have done a top end job? That takes some know how. Assuming there are no air leaks, timing is set correctly, you are getting good fuel flow, etc., lets address the carb again. Did you actually take the carburetor apart? Visually it may appear to be clean, but there are many very tiny orifices that can get clogged. Especially if it had old gas in the tank. Take it apart and spray all parts (except anything made of rubber) with carb cleaner. Make sure that the main and pilot jets are not clogged. These must be removed in order to inspect them properly. After cleaning with carb cleaner, blow out everything with compressed air. Replace gaskets if needed, check your float level, and re-assemble. What did the spark plug look like when you pulled it?