92KK 84WW Olaf
Life time member
Number of posts : 7954
Batteries can be tricky. When I got the LT I did quite a bit to it and the battery was checked as being ok.
6 weeks later up the west of Ireland on a Friday morning no go and not a motorcycle shop never mind a BMW one anywhere. Battery kaput. Anyway my only option was a ride on lawnmower outlet about half an hour away. Not expecting much I took the old battery with me and put up on the counter with a timid 'would you have one of these?' The man reached under the counter and lifted up a battery 'you mean like this?'. A perfect fit and all problems solved. My car was the same, anything dodgy on the battery and all would go mad. Usually the dealer charge for the diagnostics to tell you the battery is kaput is more than the cost of a battery. Lawnmower battery as dirt chap and it performed perfectly.
RickG is very right about a low battery.
If you can do it and haven't already done it you should open every electrical connection and clean it up. That includes the earth points. Its easy to do without the wiring diagrams if you take it methodically one connection at a time. With age they get corrosion and deposits on them that act as insulators. Clean up all the connections at the ICU unit under the seat and up at the headstock at the front of the gas tank. Dodgy connections can make a good component or sensor appear to be faulty so it is very important to get these sorted before going down the road of replacing too much. There are plenty of recommendations about fitting headlight relays rather than run the current through the switch, this may have been done by a PO. Also most important that brake fluid is changed regularly as the ABS units don't like lack of maintenance.
If you haven't done it you should replace the high pressure fuel lines as they perish with age. Same with brake pipes. Tyres go hard and horrible, 5 years is tops and 3 years better. Some bits actually suffer more from lack of use because of a lack of constant movement and corrosion.
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1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles.
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 51,800 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 63,390 miles
Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500