Losing Battery Charge

[aircooled5]

Hello all,  Finally found you guys and hope you can give me some advice.  I'm on my 2nd K75 which is a 1993 K75S.  We started off fine with a bike that looked well cared for and vendor claimed to have it serviced by same guy every year.  It had not be ridden much in past year.  However after a few rides, discovered the battery not being charged.  Checked the battery and removed it to have a load test.  Not good so purchased a new battery.
 After charging it up, she fires up immediately, shows 12.85 on multi and 13.8 at 2,300rpm.  I went for a ride to join other vintage guys for breakfast.  Came out 1 hour later after breaky and discovered it would not start....just a few clicks from the starter.  Hauled it home and re charged.  Again shows on the multi meter the right figures.  The battery is new.  Everything appears to be buttoned up and tight...battery connections etc.  When ridden, there are no lights on the dash to indicate low or no charging.  Mysterious. 

[Duckbubbles]

The charging voltage should be 14+ volts at anything above idle.  Could be alternator problems.  Worn brushes or failed stator winding.  Also check the alternator connection for good contact.

Frank

[Ingo]

I had that problem, got 6-8 miles and bike stuttered and died. No starting power. Had wife come with car, took battery home and charges, re-installed at roadside, disconnected headlight and got home. No red light indication either. Took alternator apart, found brushes at wear limit. unsoldered wires and re-soldered a bit further out. Didn't help. took everything apart and checked field coils, rotor coil, diodes, everything I could. Ordered new regulator (contains the brushes). Put complete alternator in vice, wired up a simulation of normal configuration: Battery, excitation circuit with signal light, power circuit to/from battery. Meters in those circuits. Driving with battery operated drill ( ac-drill would do just as well) I could feel the resistance of power being produced but not charging battery. At low rpm's very little resistance and charging light on. At higher rpm's the charging light went out, the resistance suddenly increased without giving proper output. Found out the hard way that not ALL diodes can be tested, there seems to be some imbedded inside the diode (rectifier) plate. Long story short: ordered new rectifier and put alternator back together, tested with same set-up and had proper operation. Installed in bike and no further issue...

[frankenduck]

Is the cluster charge light illuminated when turned on but not started yet?

[aircooled5]

Thanks to all for your useful advice.  I'm curious about the alternator but hadn't considered the rectifier.  I have some time Wednesday morning to have a good look at connections.  The charging is very close to 14 when reving at 2300rpm and there are no lights on dash indicating low charging.  The cluster charge light is lit up when the ignition is turned on but not started. 
At the moment haven't got a shop manual but a friend is lending me his.  Love the bike but this is quite different experience from previous K75S which ran without any problems for several years. 

[Laitch]

At the moment haven't got a shop manual but a friend is lending me his.

You can download one from Motobrick here.

[aircooled5]

I get this message when attempting to download a K75 manual>>>An Error Has Occurred!
The topic or board you are looking for appears to be either missing or off limits to you.

 Not sure what I have done or not done but something isn't working.  Is there a donation req'd? 

[Ingo]

Let's start with the basics: a bicycle dynamo, works by rotating a permanent magnet  around a coil. this induces electricity. The electricity is proportional to rpm's, so this is not usable for motorized vehicle. In our alternators the permanent magnet is replaced by the electric magnet in the rotor. This is controlled thru the regulator and adjusts the magnetic field as needed. When ignition is turned on but engine is not turning there is no "ROTATING (permanent or not) magnet", therefore no induction. So the regulator sends battery current (thru the red "charging" light to the rotating coil and when the engine starts the alternator generates electricity.

Once there is sufficient voltage the regulator uses the generated power to feed the rotating magnet and the red charging light goes out. It is actually NOT a charging indication, more a NOT charging indicator. The rest is just fluff: three windings in the stator generate electricity, actually 3 phases, then gets rectified into DC. The regulator uses this DC voltage to control the "excitation" of the rotor thru the brushes. The red light serves to limit the current thru the rotor and indicates the operating condition. So the red light should be on when ignition is on but engine not running. If it's out at that point the "charging" (EXCITATION) circuit is open. that could be bulb, brushes, rotor coil, grounding etc. The red light should be off with engine running but might be still on until engine reaches a certain speed (like 1000rpm) - then it should go out and stay out. But that only says there is no more battery power used for excitation, it does not mean "everything is good". Ultimately the red light only provides some limited info...

I had good success with setting up the alternator in a vice and wiring up with the bikes battery, including the excitation and driving the alternator with a hand held drill... See above somewhere.

[Laitch]

Not sure what I have done or not done but something isn't working.  Is there a donation req'd?

No donation is necessary, aircooled. I successfully downloaded it. Your difficulty could be your computer or phone security settings. I did get a warning but overrode it and downloaded the manual.

Go to BSK and see if you have success downloading their copy. You'll find it in the Service Manuals section of their download area.

[Laitch]

But that only says there is no more battery power used for excitation, it does not mean "everything is good". Ultimately the red light only provides some limited info...

Usually, the red light On means that the battery is losing charge so you'd better do some exploration into why it's on, or put on your walking shoes. 

[Ingo]

As you says: usually. In my case the red light didn't come on, yet all the generated electric was burned up inside the alternator. So the light doesn't tell it all. Red light on with engine running normal DOES indicate an issue, and DOES mean you're running on battery. And the K's are NOT meant to be electric bikes...

[Laitch]

As you says: usually. In my case the red light didn't come on, yet all the generated electric was burned up inside the alternator. Red light on with engine running normal DOES indicate an issue, and DOES mean you're running on battery. And the K's are NOT meant to be electric bikes...

The effect of ancestral curses and other anomalous conditions do take special effort to remediate, as you have clearly articulated thoroughly in your post.  Maybe the previous owner washed the alternator's interior parts with soapy water in a fit of tidiness and the effects were time-released.
 

[Ingo]

of course, on 30 year old bricks the fault time delay has long since expired, anything can (and will) go wrong at ANY time...

[frankenduck]

Even though the battery is new it would not hurt to take it to an auto parts store to have it load tested. (They do it for free.)

[Laitch]

of course, on 30 year old bricks the fault time delay has long since expired, anything can (and will) go wrong at ANY time...

That would seem to make them like everything else in life. 

[daveson]

I get this message when attempting to download a K75 manual>>>An Error Has Occurred!
The topic or board you are looking for appears to be either missing or off limits to you.

That's the same message I get if I've forgotten to log in first.

[frankenduck]

No login required at this link to get manuals  - both rider(owner) manual and BMW service manual:
http://bit.ly/new2kbikes

[daveson]

Your problem sounds similar to a problem I've had. When riding at night (away from city lights) the charge light would glow, but only very faintly, it wasn't noticeable at daytime.  One day it wouldn't start. The problem was a worn brush in the starter motor. I'm also thinking your charge rate is too low.  I would put it in third gear, roll it backwards and drop the clutch, do it a few times. If the charge rate improves, that would make it seem like the starter brushes were dirty, and probably worn. It might be worth getting the service history of your brick, if you can. I realise this guess sounds like a bunch of crap, and it could well be, but it's an easy thing to try.

[aircooled5]

Well time has passed.  Saturday finally took the battery to an automotive shop for load test.  Turns out its a defunct battery after less than 3 weeks.  Needs replacing says the read out.  Even when fully charged, it's been losing significant charge to the point it wouldn't start the bike after sitting for several hours after being fully charged.  Didn't think the problem would be with such a new battery so have been considering everything else.  So Tuesday we're going back to the bike shop.  When this battery was ordered a couple of weeks ago, I chose the Yuasa.  However when picking up the partially charged battery several days later, it turned out to be a no name battery.  On questioning this, they said that they couldn't get one and so here you go.  No one thought to call me and say are you ok with the alternative option.  I've been going to this shop for tires etc for years.  I'm a bit ticked, esp since a search on line has revealed that there are Yuasa batteries available and many other choices including Odyssey.  Not happy.

[The Mighty Gryphon]

Did the shop charge you for an Odyssey battery?  And then give you a Yuasa?  I would think they owe you the difference in price not to mention a new replacement for the one they gave you.

[Bmwsquirl]

Batteries from Napa are deka USA made labeled Napa agm.

[Past-my-Prime]

I’ve bought batteries for both my bikes on Amazon - quick delivery, prices good, you get what you order.
Lithium something for the K, and a YUASA for the F

[aircooled5]

Time has passed and now we're moving forward.  Returned the dud battery and the shop managed to source a proper Yuasa battery with the right configuration.  Its holding charge and the charging system is working.  Further searching with help of friend with Electrical Engineering background and we located a bad 4 way hazard switch.  Connection came apart and so we removed the fuse and ordered a new part from Moto Bins. The bike holds a charge and runs great. The replacement hazard switch plugs into the turn signal/hazard flasher relay unit under the fuel tank.   I'm reluctant to undo everything (1993 K75s) and lift up the fuel tank for access to the 4 way hazard relay box.  If a competent mechanic takes an hour or so to do this job, I'll take all day or more.  Am I crazy or is it easier than I think?
PS:  Also downloaded the manual successfully though its a bit short on detail.  Ian in Toronto

[The Mighty Gryphon]

You don't need to remove the fuel tank.

Lift the seat(make sure to put it back down before the wife uses the bike ) Remove the clips that secure the rear of the tank and lift it and pull it back slightly.  I block it up with a chunk of 2x4 about 3 inches long.  That should allow you to remove the relay box cover and and get at the stuff inside the box.

The fairing is designed to let you remove the tank without having to remove any fairing panels.  Lifting is also accommodated.

[aircooled5]

Thanks Gryphon for advice on lifting seat, find clips and lift tank to access the box for the flasher plug in.  I'll report when I actually get to it.  Ian