Diode board issue ?

[dlearl476]

In a fit of rushed stupidity, I took my timing cover off without undoing the battery. So of course I shorted a hot lead to ground fighting it back on past the horn mount (which I was also in too much of a hurry to remove!).
All appeared OK when I got it back together, although it did start a little harder than usual. Went on a 200 mile ride and all seemed well until my starter went "click" after lunch. Started fine on the kick (gotta LOVE /5s) but I'm wondering what I've done. Any guesses?

I'm at work so I couldn't check anything out, but I'll check all the connections first (coincidence is the bane of troubleshooting) to make sure it's not simply an air gap. But my electrically feeble mind expected a) gen light NOT to go out when I started it or b) battery to run down while riding. I did have time to check the batt prior to hooking it to the Battery tender and it was 12.5 V, which should be enough to run the starter.

Ok Gurus-What say you?

[James.A]

The short answer would be that I think you have lost your diode board. The long answer as follows:

By the nature of their material make-up, the diodes are the most electrically fragile parts of the charging system. I lost a diode board once when the small wire broke loose from the positive battery post. Any abrupt or moderately violent electrical disruption can damage a diode. Having said that, there are a lot of ins and outs to airhead electrics.

DISCLAIMER; I am not a pro mechanic nor do I fully understand the finer points of the engineering and science of electricity.

A fully charged 12 volt battery carries a surface charge of 13.5 volts or slightly higher. 12.5 is a little low. The outside air temperature affects the efficiency of the electro-chemical function of a lead/acid battery. Low ambient temperatures degrade the battery's ability to deliver current for starting. Early airhead electrical systems when functioning properly are just slightly better than adeqaute to hold up your battery. A battery dies a slower death with a bad diode board than a dead alternator or voltage regulator because the bike will run on non-rectified(AC)alternator output. On a /5, the discharge light might not glow bright enough to see it in the daylight at 12.5 volts. The discharge light gets brighter as the battery gets weaker.

If your starter does not respond to the start button at all, try this. Lift your tank and pull the blue wire out of the anti-restart relay. This relay is on the left side of the frame backbone opposite the voltage regulator. If the starter spins the engine, this would indicate an open circuit in your alternator rotor.

If your starter engages but does not spin the engine,you should hear the ratcheting noise of the starter solenoid cycling. This indicates that the battery is not delivering enough current for the starter motor to overcome the engines compression. Most likely a weak battery and/or a starter motor suffereing from aging, or both. 12.5v ought to roll the starter unless it's old and tired, but that is not likely to be the main problem in this case.

[dlearl476]

Thanks James, I'll give it a shot when I tear into it. Between a BMW mechanic friend and the IBMWR tech pages I've got a few things to check. He suspects a funky starter solenoid. (Which your suggestion would check as well)
But that was before I took it off the charger, tried it again on a fully charged (13.5V) battery ("click") which then registered 12.5V I'm thinking I may have also fried a cell in my battery (3 month old Westco, so I'm resonably certain it's not age related).
Can't get to it until next week. Thank goodness for multiple bikes!

[flash412]

Sometimes the brushes inside the starter get worn and need to be replaced. Sometimes you need to pull the armature out of the starter and rub the area that the brushes contact with a pencil eraser.

Assuming your starter, solenoid and battery are all just fine, you might have a duff starter protection relay. That's one of the tinfoil boxes under the tank. You can figure that out if you discover that your starter works when you short the BIG +12V wire on the starter to the little one on the solenoid. If it works when you do that and not when you mash the starter button... it might be the SPR. Then again, you might just need to CAREFULLY disassemble the button itself and clean the contacts.

[James.A]

The starter protection relay and the anti-restart relay are, in fact, the same part. It is a Bosch relay that serves as an analog logic device. Funtionally, it detects alternator output and disables the starter circuit to prevent engaging the starter while the engine is running. Pulling the blue wire defeats the SPR. On my bike, it disabled the starter when the alternator rotor went open and there was no continuity thru it. I don't understand why that is, but I saw it with my own two eyes.

Flash 412 got all over me on the starter testing. Brilliant strategy, using an eraser to dress the armature. Well done! The combination of a tired starter and a weak battery could easily yield the problem as described. If simply engaging the starter dropped the battery voltage from 13.5 to 12.5 without the engine starting, I'd be looking at the battery. 12.5 volts ought to at least roll the starter a little, so I'd think that the starter/solenoid might be struggling as well.

Jumping the solenoid between big terminal and the small terminal should produce the banging sound of the solenoid engaging and make the starter spin. This test would by-pass the bikes wiring.

Jumping the big terminal, or the battery positive post to the nub where the solenoid attaches to the starter motor would by-pass the solenoid and energize the starter motor directly. This test identifies a failed solenoid if the previous test does not engage the starter. A healthy, fully charged battery is essential for any electrical diagnosis.

Aren't electrics fun?

I still think Bosch electrics are better than Lucas. I loathe Lucas electrics.

[dlearl476]

Thanks guys, you've given me a bunch of things to check next week when I get time. FWIW, a buddy was in town and I lent him a bike to go riding. We WERE gonna take the R, but I decided against it due to the problem. So I'm explaining it to him, AND IF FIRES RIGHT UP! There's definitely some juju, but probably just age related. (35 year old bike just out of 10 year storage remember)
BUT, I did do something funky. This morning it fired right up again so I figured I'd take it to the Post Office and bank. I noticed half way there the ign light isn't coming on at all, even down to a stall (I checked). The neutral light isn't working any more either. Then again, these could all be completely separate issues.
I guess I'll be reading my Workshop manual on the plane tonight! And doing the /5 electrics master course next week.

>I still think Bosch electrics are better than Lucas. I loathe Lucas electrics.

I've owned a plethora of English cars (and Italian) and it's all about taking care of them. They just seem to corrode more and that's really harsh on electrics. This deal was entirely self-induced. I ain't pointin' no fingers nowhere!:brow

[CustomSarge]

Just for grins, I'd pop the metal can off the starter relay & decorrode the contacts with 600-1000 grit paper. After 10 years, it probably doesn't make a low impedance connection everytime. I also use the 1000 grit on commutators, as erasors can leave bits of soft rubber to melt/goo up things if not cleaned off well. $.02 & out <<<)))

[dlearl476]

Originally posted by CustomSarge
Just for grins, I'd pop the metal can off the starter relay & decorrode the contacts with 600-1000 grit paper. After 10 years, it probably doesn't make a low impedance connection everytime. I also use the 1000 grit on commutators, as erasors can leave bits of soft rubber to melt/goo up things if not cleaned off well. $.02 & out <<<)))

Yes, the first step will be going through every connector on the bike with ProGold (http://shopping.netledger.com/s.nl/c.ACCT113328/sc.2/category.178/.f) then I'll break out the MultiMeter and have at it.

[Braddog]

Originally posted by CustomSarge
Just for grins, I'd pop the metal can off the starter relay & decorrode the contacts with 600-1000 grit paper. After 10 years, it probably doesn't make a low impedance connection everytime. I also use the 1000 grit on commutators, as erasors can leave bits of soft rubber to melt/goo up things if not cleaned off well. $.02 & out <<<)))

Keep some emory boards (for finger/toenails) in your tool box for cleaning connectors. The narrow, fine ones work best. They work better than paper because they're rigid, and you can just use them like a file.

[dlearl476]

>They work better than paper because they're rigid, and you can just use them like a file.

I use emery cloth, or an ignition file. (But the cloth doesn't work for squat on my toes!):bliss

[nrpetersen]

Don't use emery boards or sandapaper on any electrical contacts. Use an ignition file, so you don't introduce grit into the contact area.

Iwould think a bad diode on the diode board (if that is the problem) could simply be replaced with a Radio Shack component. I've heard some horror stories on the cost of a new board. The components are cheap and very generic.

If you have access to an oscilloscope, check the output waveform to see that all three phases of the alternator output are getting to the battery. If a phase is missing, the charging system will be frustratingly weak and your battery will only be marginally charges. A headphone with a capacitor in series would also tell you if all phases are working, though I have never tried it.