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Old 06-08-2010, 06:05 PM   #1
japhyRIDER OP
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Joined: Mar 2009
Location: MT. CO. VT.
Oddometer: 6
Airhead electrical advice please

Yeah I know it's the same old tune but my bike has an electrical issue and I need some help. the patient is a beautfiul 1984 R80G/S new to me last year. I put a lot of work in it about 400 miles ago which I'm sure is the source of the problem.
I have a short somewhere. I'll be riding along at higher RPM (don't trust the tach on my Trail Tech, but it usually happens changing gears or around 75mph, so I'm thinking around 4k). I installed a digital voltmeter and once caught a scary jump to 16V just before lost all power. All the other times the Voltmeter was reading 14.1 or 14.2 and then everything went out. I've put the Enduralast system in if you're wondering why these numbers are so high. The regulator/rectifier is out in the breeze and doesn't feel like it's over heating, I haven't blown the fuse in that system either. Usually I'll have no power for around 20 seconds then everything will come back. I'll hit the starter and go on for another 15 to 100 miles before it happens all over again. Then in the course of 60 miles it happened 6 times and the third I lost the starter. The relay will click but that's it. Kick started (I know not too smart) the last few times and then lugged it (55mph 5th gear) to keep the voltmeter @14 and made it 20 miles no problems.
My plan is to pull the tank, covers and have a look at all my charging connections, and wires in particular on the starter which I figure is probably loose. But elsewhere I'll still have power since It rode home fine (sans Starter) so the lamp won't help. I know these types of threads can be painfully difficult to get involved in especially with a novice like me, but if you've got two cents to throw at me I'd appreciate any thoughts. Thanks
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Old 06-08-2010, 06:30 PM   #2
Beemerguru
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You sure it's the charging system that's in trouble and not the engine running part of the equation?

If you had a tach hooked up when the bike quit at speed, take a quick glance and see if the tach instantly drops to 0..you didn't say if it backfired or not on restart. The voltmeter feeds off the coil so it going to 0 works the same as the tach...not charging but engine management.

Those are classic symptoms of the bean can imminent failure..or possibly coils going bad.

I'd start with that direction first and see what you find.

And 14+V is a little high especially when you know you loose a volt or so through the hookup of the instrument. You wouldn't happen to have an adjustable voltage regulator do you...maybe set for city low speed riding?
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Old 06-09-2010, 05:24 AM   #3
StephenB
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You are describing part of a recurring problem with your charging system that sounds like something I have experienced: I had a crack in my diodeboard, that opened up when engine cold (no charging) and closed after 2-3min of the engine running (charging voltage present). Although the symptoms you're describing are different, there are similarities.

Now, can you actually reproduce the problem repeatedly? 15-100mls between occurrences is like every 15 to 90min. That does not sound like a temperature problem (rotor openeing up) or kill switch problem problem.

Ignition related: it could be the bean can with a temperature-/time-related problem but it wouldn' t neccessarily pull the voltage down to 0V.

The jump up to 16V and then out: good chance for the voltage regulator being the culprit for that phenomena. Cheap part: look into the dark secrets thread for alternate parts. Buy it and try it.

Checking connections is a good start. If you had an oscilloscope check the three phases of the alternator stator.

Loosing your starter: could be a coincidence. Can't see the relation here.

Try to reproduce the problem and then change parameters.

Without any more data, you could be searching for a long time.
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Old 06-09-2010, 05:41 PM   #4
japhyRIDER OP
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Location: MT. CO. VT.
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Thanks for the help guys,
Beemerguru:
You sure it's the charging system that's in trouble and not the engine running part of the equation?

Pretty sure, all the instrument lighting and headlight go out when I lose power.

If you had a tach hooked up when the bike quit at speed, take a quick glance and see if the tach instantly drops to 0

The tach is in an aftermarket computer, but it's wired in to where the BMW one would go in the headlight. While the computer has it's own battery & stays on the tach impulse quits when I lose power. The voltmeter is a digital one and it just turns off.

you didn't say if it backfired or not on restart.

The first few times it happened it was very short in duration, I didn't lose power for long and i thought it was a gas problem, gave it throttle and got a backfire. If I leave the throttle alone when it quits, I get a clean start.

14+V is a little high especially when you know you loose a volt or so through the hookup of the instrument. You wouldn't happen to have an adjustable voltage regulator do you...maybe set for city low speed riding?

The Regulator/rectifier working through thyristor ( kind of diode i think) is suppose to have a threshold of 14.2 when read from the battery they're supposed to quit. It's not adjustable but I still get 14.3 at high rpms, which does sound like too much. My battery is 6 months old and was well maintained on a tender over the winter.

Stephen B:
can you actually reproduce the problem repeatedly?

That's the problem I can't, the bike ran fine the last twenty miles and I bet if the starter worked I could start it right up no problem. It seems to only happen as High rev's and I'm hesitant to try and recreate that parked even with a fan (it's hot in Grand Junction CO). even then I'd only have 10 to 20 seconds to trouble shoot until everything's back up.

The jump up to 16V and then out: good chance for the voltage regulator being the culprit for that phenomena. Cheap part: look into the dark secrets thread for alternate parts. Buy it and try it.

It's an aftermarket system with the diode board meshed in with the regulator, so the alternate parts aren't going to work, but if I can't find anything obvious with the wiring I might have to try a new one.

Thanks again for the help.
tommy
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Old 06-11-2010, 06:20 PM   #5
japhyRIDER OP
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Location: MT. CO. VT.
Oddometer: 6
Hey folks, feel like to boy who cried wolf here but it turned out to be the positive connection on the solenoid was loose. thanks for the help though, I'll look things over before I bother everyone next time.
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Old 06-12-2010, 06:04 AM   #6
Jasper ST4
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At least you didn't replace the battery.
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Old 06-12-2010, 08:55 AM   #7
coastranger
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Joined: Jun 2009
Location: coast range oregon
Oddometer: 430
glad it was a simple fix, simple is good

dont worry too much about crying wolf, as it is through others advice that I learn so much more about the bikes, even if the hlep was "not really needed"
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