The tach is fired by the TCI, number 2 cylinder if I remember. I would suspect the TCI or the vacuum advance being defective. The TCI is different for the '83 and can only be used on the '83. The vacuum sensor is under the battery under the coils next to the TCI.
I would highly recommend updating your TCI with an ignitech unit available from member Dingy if the TCI proves out to be the failure. Check the pickup coils and all electrical connections to it and the TCI as well as the vacuum line to the sensor...
Jeff is correct! The problem with higher output stators is with more power, more heat is generated. Heat is the enemy of insulation on the wires which is the main source of failure, the windings either shorting out to each other or to ground...
Contact Earl, Skydoc_17 who makes them. Shipping to the UK might be pricey but maybe shipping via Canada may be cheaper. Earl could ship them to me and I could take them to Canada and have them shipped there if it is cheaper...
Here ya go, straight from our "Read Only" tech library...
http://www.venturerider.org/forum/showthread.php?t=508
and this...
http://www.venturerider.org/forum/showthread.php?t=2922
Angel, make sure you are using an JIS tip on the screwdriver!!! The angles are different on Japan Industrial Standard screws and if you use an SAE tip you will strip out the screw head!! Harbor freight sells a nice set of JIS impact screwdrivers...
What Jeff said!! I've been watching this thread and I too am wondering how the tests came out yesterday!
Best wishes and prayers for you my good friend the world is a better place with you in it!