I just bought a 300ex with a 30 over bore rejeted and a dg exaust with header and its burning oil and the timming chain is making noise. i want to get the motor redone . whats the most i should bore? and what all should i do to it? bigger carb?

 

give advanced machining a call and they will set you up for a great price look in the dirt wheels magazine for the # i had them do my atv work and there great
get a 36mm mikuni flat slide carb
i would bore it 78mm over or 76mm one of the 2 cant really remember and get 111/2:1 compression so you have the opption on running race gas or not

 

can I get a big bore kit for that bike?

 

yes they hook you up with everything and i mean everything for an engine