Motor shuts off suddenly !

40427 · Jan 31, 2012

1985 R80,
Just replaced the rotor with one from Motorrad Electric , bike ran fine before I did that. Planned to take the known good one along on a trip this summer.

Today I am riding along and the motor suddenly dies, no lights , no idiot lights, nothing.
" Repeated this 5" times by the time i got home, needless to say i am a bit put out and my riding buddies are not too happy with me and my machine. ( they will get over it, i may not !)

The bike does not act like it's a fuel problem, just quits running, no stumble, no stutter, just dies with no lights showing on the dash.

I can fiddle with the stop/run switch on the right grip side ,and the ignition switch then it starts right back up again ??
Happened in traffic at a congested turn, scared the ba- jasus out of me getting out of the way of the soccer mom's.

Suggestions where to start looking???????????????????
Thanks, Doug

mneblett · Jan 31, 2012

First, easiest check: Check your battery connections -- total blackout is usually the sign of a loose ground terminal or loose connection at the tranny breather bolt.

Many other possibilities to discuss, but this is where I would look first.

barryg · Jan 31, 2012

If you can fiddle with the switch and then hit the start switch and it runs , maybe the switch is defective. Take it apart as far as you can and spray clean it inside with some contact cleaner. That might get some more life out of it.

44006 · Jan 31, 2012

Where to start - start with what you disturbed during your rotar replacement

1) you disconnected battery before opening front cover - did you get the battery
wires back on and tightened - are the terminals clean - are the wire end lugs firmly and cleanly attached - is the ground wire firmly and cleanly connected to ground as well as to battery?

2) rotar itself probably has nothing to do with your problem but did you disturb the
large red wire attached to diode board while in there? This would stop charge current from getting from alternator to battery but would not make all go black.

3) My wire diagram shows 2 fuses in this bike are they good, clean,and firmly in place?

4) did you have tank off? if so check anything you might have disturbed in wiring close to inside of tank tunnel

mneblett · Jan 31, 2012

Something to keep in mind: the OP reported total black out, not just engine dead.

That means it can't be just the kill switch.

3 most likely possibilities for total black out: (i) loose battery connection, (2) ignition switch failure (or break in main power wiring leaning to it), (3) problem at main power feed at the starter relay.

ebeeby · Jan 31, 2012

mneblett said:
Something to keep in mind: the OP reported total black out, not just engine dead.

That means it can't be just the kill switch.

3 most likely possibilities for total black out: (i) loose battery connection, (2) ignition switch failure (or break in main power wiring leaning to it), (3) problem at main power feed at the starter relay.

It has to be something that was disturbed during the rotor replacement. Battery cable - or - pinching one or more of the wires under the front cover.

donbmw · Feb 1, 2012

I have had the same thing happen to my 75 R90/6. Would hit a bump and the motor would quit like ran out of gas and then pick back up. This happen 3 or 4 times over a long period of time. Then come home from work a night had all the lights go off and on a couple times. Check for some loose connections did not find anything that seemed loose. After this went to town and notice no lights working at all. Came back and starting look somemore and found nothing. But the starting noticing that at times I would have not power to anything for lights and starting. Went back and cleaned to bare metal at all gound attach points and have not had any problems since.

Don

wecm31 · Feb 1, 2012

mneblett said:
Something to keep in mind: the OP reported total black out, not just engine dead.

That means it can't be just the kill switch.

I'm not so sure....

My bike is currently in many pieces (long story) so I can't pop out to the shop and check, but.....

I am pretty certain that on my bike if the kill switch plug is loose, then its all dead, no lights, no noise, nuttin'

Its actually happened to me post maintenance. In on/off with the tank and moving the bars back and forth, the harness plug under the front right part of the tank backed out half way. Trace the wire bundle from the kill switch and check the plug is fully seated.

jad01 · Feb 1, 2012

When I had a bad connection at the starter relay, I lost all power... very similar symptoms... running fine then quits suddenly, odd behavior when troubleshooting the problem in the garage, etc: http://forums.bmwmoa.org/showthread.php?t=52453
It turned out to be corrosion at the starter relay at the power wire from the battery, which I am learning is pretty common.

Disturbing the wiring and/or changing other components (rotor) may have just uncovered a lurking continuity problem that would likely have surfaced later anyway. In any event, it's a relatively easy thing to check.

bikerfish1100 · Feb 1, 2012

worth noting the issue with OEM cracked original coils, but a cracked coil will not produce a total power shut-off, so in this case its a bit of a red herring.

lkchris · Feb 1, 2012

The 100% certain result of following the inane MSF convention of always shutting off your bike with the kill switch is a broken kill switch. Me, I always know the kill switch is not the problem because I never use it. I promise I will if I ever fall down.

40427 · Feb 1, 2012

Well , I tore in to the buggar this morning. Don't see any obvious problems, took the kill switch housing open, clean dry and tight, gave it a shot of CRC.

Same with the fuze block under the seat ( don't remember the last time i saw porcelan fuzes)

Disconnected the battery and cleaned that, pulled the front cover , checked for pinched wires nada ??
cleaned up a small amount of oily dirt on the bean can, gave everything a shot of CRC.

Started right up , rode around the neighborhood, turned the bars lock to lock nada.

Pulled the ignition cover , all clean dry and tight, gave it a shot of CRC .

Stumped at the moment.

Thanks to all who chimed in with suggestions.
Doug

jforgo · Feb 1, 2012

I had this happen with my R65. It has the ignition key switch on top, I think your mono R80 is like that (?). Anyway, it turns out the internals of the switch were disintegrating. A different speed, and therefore vibration; going over a bump; heavy crosswind; barely touching key; any of these would kill the motor, and everything else.
Play with the key and switch, ever so sligtly tapping and bumping, horozontal and verical, and see if this is where your problem lies.

40427 · Feb 1, 2012

Hmm, that could be the culprit.

I was using the BMW flat key up until recently, then switched over to a standard blade type that came with the bike and a leather key fob.( it was hard to find the flat one in my pocket sometimes)

Did you replace the entire switch assembly ??

wonder if they are still available from BMW ??????????

beemerguru · Feb 1, 2012

Bean can going out. Especially if you've eliminated the kill switch. If it happens again and you have a tach, watch the tach and if it falls to 0, the can is failing.

40427 · Feb 1, 2012

I did notice the tach was acting a bit odd when the bike died.

I only caught a glimpse of it since i was in traffic and trying to get out of the way when it happened , but i think the tach needle went way up then back down for an instant.

When i had the front cover off today i did see some oily smutsch on the bean can.
how the heck can you test one ??

Crikey I wonder how much a Bean can costs. ??

donbmw · Feb 1, 2012

There is also a main wire harness ground under your tank where the coils mount. Check and clean that one. That ground got my power back.

Don

mymindsok · Feb 1, 2012

Your bike is at least 34 years old, so I'd check the wiring.

The day after I received my resto rod from the mechanic who did the finale going-over, it acted just as you described. The issue turned out to be the ancient hot wire that goes from the Diode board to the starter. On the outside it looked great but internally, it was broken.

Start looking at the wiring and replacing anything thats old easy to get at including the grounds. At least clean em and add a dab of dielectric grease. The real key to your dilemma is that everything is going dead. That eliminates a lot of other possibilities right off the bat.

Somewhere along you'll find the problem and your bike will be much more reliable.!

20774 · Feb 1, 2012

40427 said:
When i had the front cover off today i did see some oily smutsch on the bean can. how the heck can you test one ??

Crikey I wonder how much a Bean can costs. ??

There are a few links in the Resource and Links thread that provide insight to the bean can as well as people who can fix them.

40427 · Feb 1, 2012

Thanks Kurt, I book marked that page .

I do not want to get in over my head with this motorcycle or get upside down financially with it.
Retired & fixed income dictates how much i can spend before throwing in the towel and just getting something newer.

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