It's probably the CDI box. What usually goes bad. Get one on-line. They sell performance units with a better timing range plus a higher rev-limiter.
'96 Xplorer 300 Aftermarket CDI box, K&N filter, jet kit, reworked expansion chamber from dirt bike, 1" taller + 1" wider rear tires, dual wenches, Rack on rear/w cargo pac, polaris box on front, Mossy Oak cover on seat, back-up lights on rear, aux. power source for GPS,"Theft deturent's", hand protectors, new clutch springs coming! Would love to find GURU style bumpers! By the way, I'm also a graduate of AMI with over 20 years of motorcycle mechanical experiance. New to quads, but the same basic engines. 2 stroke or 4 stroke!