ok bought a 2005 yz250f had been sitting for awhile got it running idealed rough some back fire then drained out old gas replaced with fresh gas put new spark plug in moter stated very high rpm little black adjustment knob on carb. was of limted use exhaust pipe glowed cherry red excessive loud back fire radiator over flowed in 2min. what did i do wrong thanks wade
Good day and welcome to Just Answer. My name is XXXXX XXX I'd be happy to help you with your problem today. For starters of the bike had been sitting you should have done a carb service to get all the crud & varnish out of the carb so fuel could flow properly & not give you that massive lean condition that you had. That is the idle adjustment screw & won't do much good until the carb is clean, set up & flowing fuel properly.
You should also have checked the coolant level before starting the bike & it sounds like you need a new thermostat or have a bad water pump.
Additionally because of the glowing pipe I would go ahead & do a valve adjustment.
So, after sitting I would do a carb service, a coolant flush & a valve adjust as well as a new spark plug & air filter. For starters.
Let me know if you have other questions based on that info.
thank you off to the shop igo ca-ching