Putting my 1984 K100RT non-ABS back on the road for the summer.
Over winter I've replaced the clutch plate, lubed the splines and changed the alternator seal, steering head bearings, fuel pipes and a service.
It started up fine and ran well but the battery needed a charge after the first ride-out and again a week after being recharged. Battery was an 8 yr old Odyssey so I assumed it was on the way out & bought a 30AH Motobatt from Motorworks. Fitted it last week and today it's flat too.
The bike runs well, all electrics work as they should.
An ammeter shows approx 0.4amp discharge with the ignition off. Pulling fuses makes no difference.
Given that the only implicated components removed over winter were the starter motor and the alternator would it be reasonable to suspect one or other to be the cause ? Bearing in mind that they both appear fully functional.
Do I hook up my ammeter in series and pull relays until the drainage drops ? The same with the starter / alternator.

Help people !

What happens if you remove the starter relay? Does this stop the discharge?

Disconnect the alternator wires and see what happens...

As you have found the bike is starting and running ok it seems everything works.

At .4Amps discharge its 10 Amps in a day so your 30Ah battery will be completely flat in around 3 days.

The only draw with the ignition off should be the clock, which amounts to 5mA or so. The suggestion about the start relay or even the start enable relay might be worth investigation. Have you added any farkles to the bike that would be directly connected to the battery (GPS, accessory charger, etc.)?

There was another thread like this recently and a relay was the problem.

Anything like gps, a charger, satnav  etc as Robmack mentioned would also draw a lot of power. .4A is about 5 watts [12v x 0.40A = 4.8W], its significant. Some USB chargers have a continuous draw if wired to a permanently live circuit.

If the relays [starter relay and load shed relay] don't throw up anything the alternator and starter would be a starting focus since you were in at those. But don't forget anything that might have been disturbed or a risk of pinching a wire.

My 84 K100RT was parked up outside for 6 weeks and fired up strongly, battery was in it and it wasn't topped up.

Pull the plug from the rear of the alternator, that is the most likely place for a drain. If no drain change then proceed as others have suggested.

good point rob


I wonder if the clock has gone and got corroded  and drawing far more than it should be ?

or another suggestion

could it be a lossy - corroded ignition switch ...ie partial connection to the park mode  for the illumination of the rear running lamp and above head light "parker  globe "  I wonder do they glow  slightly ...not noticed at daytime at all

interesting issue

ShedBob wrote:....
Do I hook up my ammeter in series and pull relays until the drainage drops ? The same with the starter / alternator.

Yes, but use the A connection first and not the µA or you could damage the meter if the current is too high.
And you need to make sure you get a good connection with the probes.

Thanks guys.
Got back at it tonight in a better frame of mind.
After blowing 3 fuses in my ammeter I realised that pulling fuse 3 dropped the current draw to zero and killed the clock. Disconnecting the alternator and the starter motor made no difference. Looked at the wiring diagram and saw that fuse 3 fed the clock and the flasher unit. Pulled the green flasher box out, disconnected it. Current draw dropped from 47mA to 4.7mA.
I reckon we're there ! I'll leave it off for a few days and see if the battery stays up.
Thanks chaps.

I helped another member troubleshoot a battery drain problem but I didn't have a multimeter with an ammeter function to hand. What I did instead was wire two 2 Ohm, 5W resistors together in parallel. This produced one 1 Ohm 10W resistor. I hooked up this resistor in series with the main battery lead. I then measured the voltage drop across the resistor to tell me the current being drawn by the load on the battery. By Ohms law (I=E/R), the voltage read across the resistor should equal the current being drawn by the load, measured in Amperes. In your case, if you did this resistor trick, you would have measured 0.047 Volts with the problem and 0.0047 after pulling the flasher relay.

Good one Rob.

ShedBob: do you have a switch for the 4 way flashers? If yes, you should have a look at it. This is the reason why the flashers unit got permanent power.

For people who have a hard time understanding the basic of electrical (Amps. watts, Volts...) Here is a good site explaining the basics of the ohms law triangle.

Hi Mr Frog
Do you mean a hazard warning switch ?
ie one that flashes all 4 indicators at once.
If so, no I don't have such a thing. Only accessory is a BMW alarm that was last used in 1992.

Robbie ;-)

ShedBob wrote:Hi Mr Frog
Do you mean a hazard warning switch ?
ie one that flashes all 4 indicators at once.
If so, no I don't have such a thing. Only accessory is a BMW alarm that was last used in 1992.

Robbie ;-)

Yes I was talking about the hazard switch.
If you don't use the alarm system, I would advise to disconnect it for now it as this could drain the battery. It is always powered from the battery but goes to fuse #5 (physical location on the bike, 5th fuse down) when the flasher unit is fuse #4 on the diagram (physical location on the bike is 3rd fuse down).
If you are certain that the circuit drawing power is the flasher unit, you should disconnect the handle bar controls and see if it makes a difference. Who knows, you may have a problem in your handle bar controls and it may send a weak signal to the flasher unit.

ShedBob wrote:Hi Mr Frog

Love the polite form of address, though it bring to mind 'The Wind in the Willows'.

Bill

Got a second-hand flasher unit from Motorworks. New ones only available from BMW and are stupidly expensive.

Plugged it in and the current draw remains down at 4.1mA.
Looks good !

Pulled the guts out of the old one and there's a fair bit of corrosion on the circuit board so I'm assuming the current leak has been here.

Aaaargh !
Pride cometh before a fall.
Problem not fixed. Fitted my secondhand indicator relay but set my meter to the wrong scale, thought the current draw was back down but it wasn't & I'm back where I started with a flat battery.
Today I have tried disconnecting all relays again, alternator again, handlebar switches, all individual indicators, entire instrument cluster (isn't it heavy !), alarm wiring, hazard flasher wiring and still I get a current draw. I even get a current loss when I disconnected the central earth point under the top frame rail.
Further investigation shows pin 15 on the indicator relay is weakly live when the unit is plugged in (0.4v) which in turn energises all the green / brown wires which work their way around to the various relays.
I'm starting to wonder if I either have a second dodgy indicator relay or there's a fault / break in the main loom.

Help !

Again !!!

CF (Mr Frog to you ) suggested disconnecting the alarm. Have you done that?
I 'd be removing it completely seeing as it hasn't been used in decades.
There have been a couple of issues reported lately caused by old unused alarm systems. 
It has permanent power and connects to the flasher relay, so a prime suspect.

Also the fact that you don't have a hazard sw is something to look at. There are 2 wires (yelow/violet and blue/white) from the flasher relay to the hazard sw. If the switch is not there, where do the wires terminate?

Re voltage on pin 15 on the flasher. The green/brown wire on pin 15 goes to fuse 7 (which comes from the LSR) and then on to the horn relay, then the temp relay and then to the anti-theft connection. Does your LSR work as normal?

This may be a silly question but if the flasher relay is suspect... do the indicators work as normal? if so I'd be looking else where initially at least.

Your suggestion that there could be a break in the harness might be on-track.

Hi Mr Kaptain

Yes the alarm's disconnected.
The hazard flasher wiring goes to an OE socket on the loom but I cut the wires to take them out of the equation.
The LSR works in that the lights etc go off when you press the starter button.
The indicators all flash as intended.
It's getting progressively weirder the more I think about it !

Robbie

ShedBob wrote:Hi Mr Kaptain

The hazard flasher wiring goes to an OE socket on the loom but I cut the wires to take them out of the equation.

Robbie

If that "OE socket" you mention is under the tank on the left, it's the Hazard Sw connector. All OE connectors are in the electrical box. (Edit: Heated grips connector is under the tank)

Where are you measuring the 0.4amp discharge?

Time to test the wiring for an earth leak somewhere.

Good luck

+1 on earths

Bad earths can do strange things.