is it a factory light, or aftermarket, and has the stator been changed?
could be that you have a light(bulb) that is is rated a little too high, it might be sucking juice from your ignition. i noticed when i hooked up my lights it has a little bit weaker spark, takes longer to warm up, although it never seemed to make it hard to start. i have a 35 watt stator, and 45 watts worth of lights!
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Le Crutan 
98 ec250 sixdays, doma, eline pipe guard, zokes shivers from a cr250,fredette racing chain slider, protaper withbarkbusters (SOLD)
 FOR THE SECOND TIME 07 EC300 polisport headlight, acerbis taillight ltr pv cover and case saver,trailtech endurance,120z fww, g2 throttle,xr chain puck:
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