Please help me my Honda 06 trx 400 ex just bought runs but keeps shutting off n white smoke coming out what is wrong ? N how much to fixx please help

 

Does it seem to be very hot when it shuts off? I would check the spark plug and see if it is running lean, as far as white smoke, that would be coolant in a liquid cooled motor, but the 400ex is air cooled, it could be burning a little oil from getting too hot, that usually is blue smoke, but if only a small amount is pulled in and burned fast, it will be more white than blue, you should be able to smell oil on the exhaust if it is burning it as well. Just start with the basics, make sure the oil is topped off, check the plug, air filter, and then you may need to start digging in a bit, like valve lash, carb cleaning/jetting etc.

 

How did it sit before you bought it. Cleaning the carb might help