Been asked to sort out an old Pro !!!. (helping out a new start.) Has overheated. Fan  & Stat tested out OK. Original Leonelli Fan AC/DC Rectifier u/s. (White 3 pin connector, Black / Red/ Yellow-earth). Replacement has arrived with a black 2 pin connector (black/ red, plus a single yellow (spade), & single white (bullet) wire. Kokusan wiring diag as per original Rectifier, so new  Rec is a bit different.   Single Yellow looks to be switched signal from stat, as per original, ( spade connector will hook up with original blue (!!!) wire from stat as per diagram. White wire I,m not so sure about. Think it might be earth, but would prefer to get it right first time. Firm believer in "If in doubt: Ask" . Have asked supplier, but Technical Support currently unavailable. Any advice greatly appreciated. 

Thank you.    

The usual reason for the rectifier getting fried is either the voltage regulator has failed (the box under the headstock) or the voltage regulator has a bad ground connection. I'm not 100% sure about the wiring. Check the voltage reg for having a good ground before hooking up and starting the bike, or install a new voltage regulator.. Bye, Peter B.

All done  Bike up & running. ? White wire is earth. Many thanks for your technical advice, & also worthy of mention is that Well known UK Chesterfield Trials Specialists  : Spl*****p. Thank you  folks. Original Fan Rec had a bad earth, so could  have been likely initial cause.