thanks everyone on the forum for your help and advice.  1 month and 1 day, k100rs back 2 life. its really a tale of going back 2 basics and never giving up. KEEP THE FAITH WITH YOUR K  AND YOU WILL BE REWARDED. after changing everything more than once, turned out to b 2 faults. firstly, my pick ups were dead. 1st replacenent 2nd hand pick ups were dead on 1 side, as were the 2nd set i got, and unbelievably, were the 3rd set i got.  is it because these things are 20 years old?. also ecu fault. engine would only turn over half a turn. WAS NOT A STARTER MOTOR OR ALTERNATOR FAULT, AS I ALSO CHANGED THE BRUSHES. 4th set of pick ups and a replacement ecu,HEY PRESTO, LIFE.  pick up fault meant spark on coils 1 and 4   on all the faulty pick ups i had. no signal from brown top sensor wire. im going to locate 6   2av54  sensors and make up 3 completly new hall sensor plates. should last for a while.   going 2 get injectors balanced b4 i take it 4a spin on tuesday. HOT TIP ON ALTERNATOR BRUSHES/REGULATOR.   TAKE YOUR COMPLETE BRUSH ASSEMBLY TO YOUR LOCAL GSF DEPOT, GET A NEW ONE FOR £11. SAVE A FORTUNE ON GENUINE PART.   also, going 2 look into 4hole injectors. take care all, and HAPPY X MAS AND NEW REAR TO U ALL

Well done Tuffty good result.

tufty666 wrote:......AND NEW REAR TO U ALL

Thanks, but my ass is still in good condition   

Most of that electrical gear is designed to only have a 10 year working life and some of the hall sensor assys are 30 years old now.  They get to the stage where heat makes them fail but when they are tested they are cold so show that they are OK. I have 4 sets and have been thinking of putting new sensors on them and  selling them exchange.. but would be very uncomfortable selling them as they are.

About hall sensor units failing when the engine gets hot enough...........

Don't know is this just is some hearsay, but remember that I've read that some have came to the conclusion that the problem is the heat shrink tubes used at the wire joints between pick ups and the wires from the connector under the tank and down.

It's said that the material isn't that heat resistant and gets brittle....and when the metal in the wires expands because of the heat, you get a short.

Could be right, with a lot of electrical equipment you are advised to leave it on all the time as it is the constant on/off that eventually kills the components.
I have found heatshrink tubing that was applies 20 years ago and it is hard and crumbling now.