Have had this sled 6 years and never has run reliably. Have a no spark/start condition that has me baffled. Had a new stator replaced a couple years ago but that never fixed the problem. Will run for a couple of days or so then come out and pull my head off. No spark or anything. Tried new battery, coil, etc. What could be wrong? Any help is GREATLY appreciated.

BATTERY,BATTERY,BAQTTERY!!!!!!! Have you replaced it. Your efi requires a battery that is fully charged, buy a new battery and spend the money for a BATTERY TENDER!! they are like $20-40. You'll only need the small one as it'll keep charged. This should be your first move if the batterry hasn't been changed.
Caleb