2003 Sportster starting problem?

I have a 2003 Harley Sportster 883. I have an intermittant starting problem. Sometimes it backfires through carb and exhaust, next it may turn over but not start(like no spark) and sometimes it starts up and runs fine. It acks as if something affects the timing/ignition. Not wet, 0r dirty

Any help?

Thanks
Update: The 2003 is electronic ignition, no points, it is not carb related, no odor of fuel, and after several attempts, of backfire/retarded kickback, spin free like no spark, it starts and runs fine. I don't know what the "cam sensor" does, or how the electronic ignition controls tioming, but it feels like... show more The 2003 is electronic ignition, no points, it is not carb related, no odor of fuel, and after several attempts, of backfire/retarded kickback, spin free like no spark, it starts and runs fine. I don't know what the "cam sensor" does, or how the electronic ignition controls tioming, but it feels like something like that is shorting, then clearing so it runs!
Thanks
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