Check the regulars. Spark plug, air filter, ...etc. It is possible that the rings are shot and there is no compression. Do you feel a lose in power or is it burning oil? Both of those are signs. It could be an electrical thing too. Try to clean up the contacts and spray some wd40 on everything.
~2001 Yellow 400ex, K&N filter with Pre-filter, POLISHED Supertrapp IDS2 silencer, 20" rear Holeshots tires, Braking brake pads, Black Shockers Shockcovers, Renthal 400ex bend bars w/ oury grips, Pro Design tether kill switch, JE 440 big bore 10.5-1 piston, Dyno Jet Stage 2 kit, Removed air box lid, Duncan Racing aluminum nerfs, AC Racing full chassis skid plate, Race cut plastic, AC Racing mudscreen bumper, and a 42 pilot jet and removed choke.
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