I have a 85 k100 and i love it but ive been having some problems with it.. the bike doesnt hold a charge. i changed the alternator (with a used one) and i changed the battery. the bike when charged starts up no problem but when you let it sit there is dies within a very short period of time.. if you put the choke on it stays running so i though if i kept my hand on the gas a bit it wouldnt shut off.. I as wrong the bike was probably at 45 mph when i shut off on me in the middle of the street, luckily it was right in front of my brothers house.. when trying to start the bike immediately after coming to a stop it tried to start but after a few time the battery (which is brand new) was dead.. I am thinking its a charging issue.. I swapped the alternator like i said previously.. I need to get back on the road and i really dont want to drop money on having my guy look at it right now since im getting married in two months and need to save up for the wedding... PLEASE HELP MY GUYS!!!

Well, best of luck on the wedding.

Don't despair on the K because this can be worked out using the experience on the site here.

If the bike is charging but doesn't hold the charge then either the battery is not holding the charge or something is draining it. The charging circuits should be ok.

If its draining quickly then there is a big drain on the current somewhere. I wonder could it be a faulty relay?

K bikes go funny if the battery voltage is low or its not fully charged so that needs to be sorted first. It might be that your other problems are caused by this.

Do you know how to go about testing for an electrical drain? You could as a start take out the fuses [behind left hand side panel] and see if that stops it happening. If it does then you know its one of the fused circuits. If its not then try disconnecting the earth terminal, if that stops it then it is an unfused circuit. No cost in doing these two. If you are using a tester DO NOT USE A SELF POWERED TESTER. without advice from here.

There are quite a few experts on the K here and some will give you more advice too. If you can get a Clymer manual it would be good.

See the thing is when I bought the bike the cluster wasn't on it.. The previous owner removed it BC it went bad

What would cause a bike to lose all power when running and then not have any to start the bike

Amohd wrote:See the thing is when I bought the bike the cluster wasn't on it.. The previous owner removed it BC it went bad

If you ain't got the charge warning lamp in the circuit, the alternator won't charge.

Is the cluster on it now? Can you post some photos of the bike?

No its not.....

ive seen a lot of k bikes without the cluster before

Install a 3W warning lamp...between the blue wire from the alternator and a switched wire.......problem solved.

So thats the reason im losing power?

The alternator won't charge....if the battery get drained when the bike isn't used ...it's another problem.

where can I find a 3W warning lamp?

You could try at a shop where they sell automotive electric euqipment.

Inge K. wrote:

If you ain't got the charge warning lamp in the circuit, the alternator won't charge.

Could be that this is valid only with the older type mechanical voltage regulator,
sorry Amohd.

That's fine thank you.. I'm just wanting to go riding.. Its about to be fall here in my part of the world haha

An 85 K without the warning light will not charge. It needs the current that lights the charge light to make the alternator start charging but once started it will self excite.
My opinion is that the battery is only partly charged and so appears to lose the charge overnight because the cold engine is a bit harder to start.
The alternator could occasionally charge due to residual magnetism in the armature but it would not start to charge till very high revs are reached and once the revs go back to idle it would cease to charge again which would account for some very sporadic charging.

so my best bet would be to connect the wires again?

just fit a globe holder that will take a wedge type lamp ...then a 3 or 5 watt globe and connect the globe as inge suggests

between a positive + wire that is switched  and the blue wire in the loom to the instrument cluster .
then you should get charge happening

I have observed with a low idle ....before getting to charge revs ( about 1200 plus ) that the whole system pulses with a low voltage being present ...which coincidentally  times well with the ignition and injector current draw .....it wouldn't take long to flatten a battery at all with all the systems in activity ...like the fuel pump and other things active whilst running .

good luck....it aint hard

Do you have the instrument cluster? The early Ks had a common problems with the cluster and most were replaced under warranty. There is some info out there on how to repair them, and I'm sure there are a few chaps here who could walk you through.

There are some other circuits in the cluster that are necessary for operation, which leads me to believe there has been some custom wiring done. This can be an invitation to Gremlins.

So  i went through the box of parts and i found the cluster and i hooked it up.. but it still did the same thing, i got a pictures that may help you help me.. Im hoping that we can get this fixed bc im the only one not riding in my town and the weather is amazing 

that main feed wire out of the alternator ...has been cooked big time

now the question is did the alternator go faulty or was there a short on that wire to the battery  taking out the alternator wire whilst running ?

maybe even a short on the starter relay ???

or just wearing through the insulation on that cable to earth

in any case it would need replacing  from the output of the alternator to the battery  to repair the loss of insulation off the cable ( so that it wont short to earth as it is always live ).....a really good inspection of all the cables nearby would also be recommended ...as I can see that the field wire (blue ) has been fused - affected  by heat some what as well .

you could put a temporary  and fused wire between the alternator output and the battery .and or measure if the alternator has a short to earth .

you could also temporarily connect up the battery to the blue wire through a bulb holder and 3 watt bulb ....whilst running and test to see if you are getting some charge out of the alternator ...use a multi meter .

those connectors in the fuse box would be a good place to pick off a switched wire and then go to the globe then the field terminal of the alternator ....using the appropriate connectors

my brother told me that he was trying to jump the bike and put the pos on the neg and neg on pos..... that's how the wire got cooked

that would do it I guess.....giggles  

wonder what else it damaged
lets hope it didn't damage the diode pack internal to the alternator .....they should survive,  supposed to be at least 50 volts piv )peak inverse voltage)
not sure if the stator wiring would survive though ...looks like it got pretty warm

when the choke is on and i have the cables jumping the bike it doesnt die immediately after i take the cables off.. but when the choke is off and i remove them it dies immediately..

what would the bike do if the starter relay has a short in it?

best to measure the alternator for a short to earth

below 1200 the alternator does not charge at all


re the short in the relay

constant power drain of battery till you remove the brown wire

you really need to do some measuring  instead of just doing the same stuff over and over again

I woke up early today and took every step needed, that i was told to do.. i put the bulb on a switch wire and everything.. I did notice something though i dont know if it means any thing  but when the alternator plug is plugged into the alt there is a charge, but when i try to see the charge of the plug when its not in the alternator ther is no charge in the plug what so ever, and another thing could the starter relay be bad and still start the bike but be the reason the bike isnt chargering????

no not likely .....either the relay works or it doesn't

no charge ? do you mean no voltage ?

the big lead from the battery should be at the same voltage both ends of the cable

the cable that I saw in the pic that you posted earlier was well burned from an extreme heat of the reverse voltage ...I would surmise that the cable is actually become non conductive .....probably at the lugs that connect at each end ...

a new cable will need to be made or purchased ....even from a wreckers ?

but I think you might need the help of a friend with good electrical knowledge

 cheers

She is running guys but she seems to lose charge at idle now, as long as im on the road she runs fine but when I park her and keep her on shes dies

possibly a diode in the alternator is dead

have seen a few of these recently ...not just on k bikes

where can i get a fully functional alternator that works?

um ...try ebay ....

they often have parts from some of the boneyard ( wreckers ) for sale with working item guarantees

the one I have on my bike is from ebay... any bmw bike websites out there?

would it be better for me to get a 50A alternator? or is the 32A fine?

Unless you intend to run a few extra electrical components like high power spotlights then the 32A alternator will do the job just fine. Take it to an auto electrical repairer or you can buy reco ones from EME
http://www.euromotoelectrics.com/category-s/767.htm