On my way across the Bay to visit my friend Greg at his shop riding my Silver '90 K75. While on the San Mateo Bridge I noticed that the turn signals weren't working properly. The right signal wouldn't turn on and the left would only blink once. And the emergency/trouble light switch when turned on would work with both sides blinking. But when it was turned off the left side would continue to blink. Got to the shop and re-tried the turn signals but neither would work. But when I turned  the power switch off  the engine continued. I tried the power switch and the kill switch. Same response, the engine would keep turning  with weird sounds. At this point Greg arrived got out a hex wrench and disconnected the main ground. The one found on the left side above the gear shifter. This stopped the engine. Notably the coolant started overflowing the small tank suggesting an overheating problem. After a few minutes we/he pulled off the side panels, the radiator surround, the master computer (one under the tray) lifted out after disconnecting the handle connector, and pulling the gas tank up a couple of inches. His analysis was that the starter relay had failed with the points probably welded together. He took a starter relay off a parts bike lying nearby and installed it. After re-installing everything and refilling the coolant tank we tested the bike and everything worked as it should. I then scrounged through the trash box and appropriated what looks like a decent rear rack that was being tossed. So with it tied on the back seat I made it back home. Once home I took the old starter relay and cut off the box so I could inspect it. The electrical points were not welded together and I have yet to test it further properly.

So assembled masters of K75/100, I would guess it was the starter relay as replacing it cleared up the problem. But I would like to confirm that so as to insure that I won't have any further problems from this quarter. What should I look for in the exposed starter relay? Or, scarily, are there any other possible explanations of the problems encountered?

Thanks for your consideration
J.

Check the contacts for minor pitting/welding. That might have been enough to stick them together until someone dropped the relay on the bench/floor.

Has your brick been idle for a fair while, or you've done lots of short trips lately, so the Volts are a little on the low side? 

Often this problem is due to low battery Voltage. Here's one way of thinking about it, the starter needs to draw a lot of power from the battery to turn the engine. If the Volts are low, well it might just draw more Amps to make up the difference. Too many Amps can make the tiny relay contacts get hot and sticky. After a good ride the Volts are higher so it's not as bad. A battery that's many years old, might struggle to provide more Amp's as well (cause the plates are all sulphated up, a smart charge can help against this) even if the Volts are good, so in that case it won't get sticky so easily.

daveyson wrote:Has your brick been idle for a fair while, or you've done lots of short trips lately, so the Volts are a little on the low side? 

Often this problem is due to low battery Voltage. Here's one way of thinking about it, the starter needs to draw a lot of power from the battery to turn the engine. If the Volts are low, well it might just draw more Amps to make up the difference. Too many Amps can make the tiny relay contacts get hot and sticky. After a good ride the Volts are higher so it's not as bad. A battery that's many years old, might struggle to provide more Amp's as well (cause the plates are all sulphated up, a smart charge can help against this) even if the Volts are good, so in that case it won't get sticky so easily.

Daveyson, You're right that I don't ride enough. I'm doing good to get out a couple of times a week nowadays. But I rearranged an electric box in the garage and have two battery tenders mounted on it so I can put both Red and Silver on a battery tender when not riding. When this happened I had just ridden out to Wendy's for a burger and had no problems starting at the beginning of the ride or at Wendy's. But I do wonder whether we can test the battery at home for sulphation or other issues. Dai's correct about the pitting on the contacts. The very center of the contacts does look rather rough. Interesting as the rest of the relay is quite pristine. Pretty actually. I'd be tempted to clean the contacts and put it back into use except that taking the box/surround off has rendered that impossible. Looking through my spare parts I don't find a starter relay which is a problem as Greg says he doesn't have another and I feel obligated to replace the one he gave me. And small parts like that aren't usually on Craigslist or Ebay.

jjefferies wrote: I'd be tempted to clean the contacts and put it back into use except that taking the box/surround off has rendered that impossible.

Huh? The cover should have just popped off with a bit of aid from a couple of small screwdrivers to prise the sides away from the base.

Dai wrote:

jjefferies wrote: I'd be tempted to clean the contacts and put it back into use except that taking the box/surround off has rendered that impossible.

Huh? The cover should have just popped off with a bit of aid from a couple of small screwdrivers to prise the sides away from the base.

Geez, wish I had known that. It resisted my attempt so I made a cut around the base with a grinder thinking it was a throw away.

Side note: When the starter relay sticks so that the starter keeps running it is sometimes possible to unstick the relay just by whacking the right rear corner of the relay box to unstick it.

duck wrote:Side note: When the starter relay sticks so that the starter keeps running it is sometimes possible to unstick the relay just by whacking the right rear corner of the relay box to unstick it.

Duck, Good One.
I know I must have heard this before but in an emergency can I remember it?

But don't you have to
1. Lift the seat
2. how to get to the right rear corner to whack it?

I'll go out and check it in a few minutes.
Got to re-glue the fan shroud mount that got broken off.

One design issue is the start relay is driven by the engine computer, so it has a quite low coil current.
This makes them prone to voltage drop release. My suspicion is a soft battery drops voltage from the starter amperage, releasing the relay. Then the starter amperage goes away and the relay reengages - OOPS welded contacts.
You can "thwack" the right rear base of relay box with a screwdriver handle or a stick, but it's behind a frame tube, my hand can't do that.

I've owned 10+ K bikes and had this happen enough to cause me to design / build a solid-state relay. Put them in last 3 Ks I owned. Tried selling them, but discovered how bad NIH (not invented here) is among BMW owners.

I've used notebook paper as a very fine "sandpaper" to resurface relay contacts.
The pitting is a matching pattern between the contacts, making them more prone to welding.
Good Hunting   <<<)))