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Hi and welcome to JustAnswer,Thank you for the question and your patience. Should you still need assistance for information purposes only...Initially, review the parts of the Yamaha that were worked on when the stator and regulator were replaced. Of interest would be the mounting/placement of the pulser coil co-located with the stator winding (even if just to rule it out as a potential suspect).
Still, the described symptom of "...back cylindor is not getting worm at all.., but dose have spark..." would appear to be a fuel delivery issue then. Proposed preliminary tries (if have not been done):