starter relay replacement (aftermarket)

[Martin]

As far as the tank "E" clips go I made a wire with a small hook at one end and a finger loop at the other end. You can also try adding a cable tie to the "E" clip and trim it so it just clears the tank. Or if you are handy make some extended "E" clips.
Regards Martin.

Tank clip prototype 1.png (16.9 kB . 768x576 - viewed 402 times)

[enb54]

Thanks, I'm open to anything that works, whoever owned my machine previously had used some kind of rubberized caulking to vulcanize the rubber washers and basically melt them into the metal, I had a devil of a time removing the fuel tank.

[The Mighty Gryphon]

I use small cable ties on my clips.  Makes them easy to remove and reinstall.  I put some Vaseline in the rubber grommet to help with pushing the tank down to get the clips in.

The cable ties also work on the clips that hold the seat, especially the clip thar holds the hinge pin at the rear of the seat.

[bmwcyclist]

In the post sited above, what happened between Step 3—the replacement of the ICU, and Step 4—the addition of the second relay? Did another OEM relay fail after you replaced the ICU?

After the 2-relay setup was installed I have had no further problems. Back to being a great trustworthy K75.

[Laitch]

After the 2-relay setup was installed I have had no further problems. Back to being a great trustworthy K75.

That I understand. What I'm trying to understand is how you are certain that failure of the relay wasn't caused by a faulty ICU.

[bmwcyclist]

That I understand. What I'm trying to understand is how you are certain that failure of the relay wasn't caused by a faulty ICU.

The relays were failing on the HOT side.

[enb54]

Thanks Martin and Gryphon for the cable tie idea, will try that out after all my final testing, had to pull the radiator to get at the fan motor, which turned out to NOT be defective, was really a wiring problem. Some people have unusual ideas about how things should be "fixed" but I guess we have all experienced that stuff, just disappointing...

[daveson]

The relays were failing on the HOT side.

Thank you for posting your interesting and workable solution.

Are you saying the failure was due to the Volts too low on the hot side? Was the cause found, like why doesn't it happen with your other brick using a weak battery?  Like maybe the resistance is higher on the trouble one?

[bmwcyclist]

Thank you for posting your interesting and workable solution.

Are you saying the failure was due to the Volts too low on the hot side? Was the cause found, like why doesn't it happen with your other brick using a weak battery?  Like maybe the resistance is higher on the trouble one?

That was an answer to a specific question about the ICU.

I own two K75, and ride with close friends that bring the number up to 5. Only the one bike ever had relay issues. It would eat a relay about every two weeks or so.

I read all of the threads and followed all of the advice:
1. checked battery power
2. replaced the battery
3. replaced the battery again
4. Replaced all related power cables
5. Added additional ground cable
6. Replaced the starter (twice), one used, one new
7. Replaced the starter switch
8. stock and aftermarket relays

None of this solved the issue. I installed the two relay system and it has worked perfect since.

[daveson]

Thanks for your detailed reply and sorry about my vague post.

While the other suggestions seem to be electrical, I imagined a mechanical reason that shows up as electrical, say friction from a tight bearing for example, resulting in a Voltage drop while cranking being lower than normal.

So I was wondering if one of the tests you did was checking Voltage drop across the battery while cranking, using the same battery with both of your bricks. That test (or an Amp test) might even set your two relay brick apart from the other four.

Just a thought.

[enb54]

I found that once they start going you will continue to replace them.

This was my final solution :

http://www.motobrick.com/index.php?topic=7704.msg124912#msg124912

After reading through that thread pretty thoroughly, I gather that you use the K75 starter relay to operate the F650GS relay to switch the high current required by the starter motor? Presumably because by itself the F650GS relay caused other electronics to misbehave? I will keep that in mind if I have problems again, but will likely get a high current relay that is less expensive than that gold plated solid platinum $$$ BMW part. The WM686 from johnny's post is only about $10 and it handles 100 A...
Thanks in advance for sharing your efforts...

[rbm]

It is possible that the coil current demand of the F650GS relay was excessive or the snubber circuit inside of the F650GS relay was insufficient to suppress voltage spikes caused by the coil, and thus one or the other reason took out the drivers in the failed ICU.  By paralleling the OEM starter relay, the correct current draw and EMF suppression is presented to the ICU and it's happy.  The F650GS relay coil can draw as much current as it needs through the OEM relay contacts to actuate and it's happy. 

It's possible that another relay could substitute for the OEM relay in this configuration if it has the same coil specs as the OEM relay. Do you know how much current is demanded by the F650GS starter relay?  The OEM relay demands about 275mA @12V.

The best solution would be able to find an aftermarket relay that was speced exactly as the OEM relay yet was the correct physical size, cheap to buy and easily obtainable (and didn't have that nasty habit of oscillating when the battery voltage is low).


Update:   I did some looking around and found a TE Connectivity Potter Brumfield high power automotive relay very similar in appearance to the F650GS relay.  This is a Potter Brumfield 2-1414939-2.  The 12V model has a 37 Ohm coil.  I measured the DC resistance of the coil of a BMW K100 starter relay I had in my spares box and it measures 43.5 Ohms.  Obviously, the PB relay will require greater current to operate than the BMW relay.   The BMW relay uses a freewheeling diode as a snubber whereas the PB relay uses a resistor.  Either or both of these differences might well be why the ICU failed for bmwcyclist.

[daveson]

Hi rbm,

Is there any merit in the thought that excessive mechanical resistance could drop the cranking Voltage to a point that causes the relay to stick? I'm trying to understand why some bricks don't have the problem even with weak batteries. Or maybe it has to be just the right amount of flat to cause oscillating.

[rbm]

Yes, mechanical resistance felt by the starter motor will cause the motor to demand more current from the supply to overcome the increased torque demand.  If the supply, the battery, is unable to meet the demand because of poor health or increased resistance of wiring between the source and the motor, then the terminal voltage of the battery will droop. 

The entire motorcycle electrical system experiences the droop, including the starter relay coil and the following cycle of events will occur should this happen. If the droop across the starter relay coil falls below its designed "Must Release" voltage, the relay will disengage, the starter motor will stop, the battery terminal voltage will recover to above the designed "Must Operate" voltage, the starter relay will engage, the starter motor will stall, the battery voltage will droop, the starter relay will disengage, the starter relay will disengage, and so on and so forth until the starter relay contacts weld themselves together because of the heat generated.

Variation in lots of variables will cause different responses.  The Must Release and Must Operate voltages vary from relay to relay because of manufacturing differences, voltage drop across the motorcycle electrical system will vary, the mechanical torque the starter motor must overcome and deliver to rotate the engine will vary, the internal resistance of an unhealthy battery will vary, and so on.

It's complex.  My K75 has never welded a starter relay ever, even with a very unhealthy battery installed.  I've been lucky I guess.

[Laitch]

My K75 has never welded a starter relay ever, even with a very unhealthy battery installed.  I've been lucky I guess.

My moto's starter relay hasn't capitulated in the 60K miles I've own it. The battery is eight years old and has never been maintained on a trickle-charger. I'd better get shopping.   The durability of some starter relays might be attributable to being in a well-tuned moto and that is cranked with a firm thumb on the starter button, and that isn't cranked for more than three or four seconds at a time.