My buddy's 04 cr 250 that he just bout is having problems it had a bad air filter and the plug was white when he first bought it I cleaned out the air box put a new oiled filter in checked the carb all the jets are clean and the right specs it used to start and not idle when u fist started it after taking apart the carb it went to idle then died I kicked it again kept it running I let off it died now it wont start at all im thinking maybe a new plug and fresh gas but not sure