1975 BMW R60/6, starter motor or switch is kaput

[motaman38]

My starter failed last weekend. I went to start the bike after filling up the tank at a gas station, and when depressing
the starter toggle it simply went "click", and nothing happened. I repeated turning on the ignition several times and the same thing happened, pressing the starter toggle switch, again and again, and it simply made a click sound. I had just finished a 45 minute ride, therefore,
the battery was not an issue (the lights did not dim, i.e. the headlight and/or instrumentation lights when I attempted the start). I am
assuming it is the starter relay or switch, or the starter motor itself?

Any helpful advice is appreciated.

Thank you,
Motaman

[schrader7032]

Motamon -

I wouldn't be too quick to rule out the battery. Often times this happens...you're riding, using the bike, stop for gas or park it at home...the next time it won't start. How old is the battery? What type of battery is it? Are your cables original...could there be corrosion in them? Could it be that the ground attachment at the speedo is loose or corroded?

I would first put a voltmeter across the battery terminals. Measure the voltage when hitting the start button. If the voltage doesn't change from say 12v, then there's an issue between the battery and starter. Could be the relay and terminals are corroded...could be a starter/solenoid issue. If the battery voltage drops below 10v, then the battery is at fault. At some point, it probably make sense to have the battery officially load tested.

That's what I'd do. Let us know what you find out.

[motaman38]

Hi Kurt,

I checked the battery voltage. It maintains 12-13 volts during starting attempts, showing on a voltmeter, with the headlights switched on. I have now removed the gas tank and seat to trace the issue to the relay and then the ultimately to the starter motor itself, if needed. I am not sure where this ground connection at the speedometer is, or could not find it? How do I check the relay?

Thanks,
Motaman

[schrader7032]

So, do you hear any clicking of the starter relay? The relay is supposed to pull contacts together with the relay and the contacts click when doing that. If you don't hear clicking, then the relay is not working. If you do hear click but the starter doesn't work, then there's a problem at the starter. Snowbum has a section on starter problems...might be worth a read:

https://bmwmotorcycletech.info/startingprobs.htm

To test the relay, you would want to look at four terminals when the relay is pulled out of the bike. Normally, 12v goes to the relay when you push the start button. Terminals 85 and 86 is where the 12v goes through. Normally, terminals 30 and 87 would show open but when 12v is applied across 85 and 86, then there would be continuity between 30 and 87. When that happens, current through heavy wires flows to the starter solenoid which then engages to turn the starter motor.

Could be that your starter relay terminals are corroded. Removing it and reinserting it a number of times might help that. Normally, the best test for a starter relay is to replace it with a known good one.

As for the speedo ground, I was probably confusing things a bit. I'm talking about the battery ground to the bike's frame. It attaches at the same spot where the speedometer cable plugs into the transmission. The ring terminal of the battery negative cable can become corroded or the bolt could be loose. The bolt shouldn't be hamfisted tight...it can strip easily, so it just needs to be snug and tight.