Odd starting problem K100 85

[Beemer01]

I've begun to experience an interesting and intermittent starting problem with my old K100 (42,000 mi).

The bike will sit for a week untouched, and will start right up instantly. I'll ride for a little while, and stop to refuel, or turn it off to get a cup of coffee and when I try and restart her, she'll barely turn over. Always requires that I bump start the engine to resume my travels.

Note - this does not seem to happen if I've been riding for a while but that may just be random.

Battery was new last year. Installed a used starter last fall.:scratch

[roy]

I've begun to experience an interesting and intermittent starting problem with my old K100 (42,000 mi).

The bike will sit for a week untouched, and will start right up instantly. I'll ride for a little while, and stop to refuel, or turn it off to get a cup of coffee and when I try an restart her, she'll barely turn over. Always requires that I bump start the engine to resume my travels.

Note - this does not seem to happen if I've been riding for a while but that may just be ramdom.

Battery was new last year. Installed a used starter last fall.:scratch

These bikes have a strange starting system that requires the starters be clean internally. You may have to pull the starter and clean the dust out of it from the brushes wearing etc.

Hopefully more knowledgeable people will give a better description of this problem.

Roy

[JamesBayles]

You will need to provide some voltage readings at various points to determine source of problem. First and foremost voltage at battery while it is symptomatic, secondly voltage at starter motor while it is symptomatic, and possibly voltage drop across battery to starter cable, and drop across battery negative to engine case (starter mounting) measuring voltage drop involves hooking volt meter leads to each end of suspected cicuit (i.e. to battery positive and to battery terminal at starter) any reading over .2 volts indicates a problem (bad connection) in circuit. Hope we can help, keep us posted.

[PGlaves]

That symptom typically indicates a bad connection that is marginal cold and worse hot. Often as a bolt warms and elongates the connection loosens enough to be erratic.

I would check and clean the connections at the battery, the connection at the starter, and the main ground on the transmission case.

If that fails to cure it I would pull and clean the starter.

[Librarian]

Had a longtime problem like that myself. '85 K100 and would start fine, run fine, and not re-start when it was warm. Of course mine would crank just fine. Turned out to be a faulty fuel pump relay that wouldn't close when it was warm. Again, it comes down to: fuel, air, spark, and then check all the wiring.