Hello from this new member. I just bought a 1985 k100rt from a guy this weekend, got it pretty cheap I think, has new Michelin tires on it,extra Russel day long seat, (very ugly seat, may sell it?),small tour pack and side bags. According to the maintenance records it's had the speedo changed once, must have around 35k miles on it at least. I replaced the fuel pump and got it running, let it warm up a bit and changed the engine oil,tranny lube and final drive, flushed radiator, new anti-freeze.

I took it for a ride sunday and it runs really good,replaced the works racer shock on it with a koni that came with the bike, the guy who had it put the shorter works racer shock on it (may sale that shock also)and lowered the front forks a little. I raised the front forks back up to the original location.

These are the issues that I'm trying to fix currently... there's a violet/grey wire laying loose in front of the air filter box, it has 12 volts on it. The violet wire as well as a brown earth ground wire had the insulation chewed off from it (rodent nest). The brown wire is clipped onto a male blade on the backside of the rail that runs along the length of the engine, just to the left of the air box. But the violet/grey wire is laying loose in there and it has a female blade type clip on it, repaired the ends that were chewed up on both of those wires, reconnected the brown wire, but have not discovered where the violet/grey wire connects at. I've felt all around in the void in front of the air box to no avail. But I have yet to check up under the frame for a blade connector, do that this morning.

According to the clymer wiring diagram the violet/grey wire goes to the Vacuum switch, but i have not discovered where the vacuum switch is. I hope the connector for this wire is hiding up above where I have not looked.

OTHER ISSUES: the 2 fuel indicator lights and high temp do not "tell tale" at pre start ignition on. (bulbs to check yet)

the tachometer will only rev up to around 3200 rpm, then it just sticks there until the engine rpm drops below that rpm.

I've looked this forum over a little and found a lot of helpful information.

thanks, bob

right? talked to Holt BMW today, the mechanic there said he thought the violet/grey wire was for a dip switch that my bike never had on it. I don't feel real sure if that is what it was for, would still like someone on this forum to chime in on this. Thanks

Bob,
Welcome to the forum.
The Vacuum Switch was found to be not necessary by BM and was removed from1986 on I believe. It was situated on the rear of the fuel rail. I removed mine on my 1984 K100 and most people followed suit. So, it appears that you are looking for something that is no longer there. I didn't remove the wire, just insulated it and It has had no noticable effect.
The biggest problem on these wonderful old m/cs is the connections...thouroughly clean and reconnect all you can see going to the instrument panel (and everywhere else)before you do any stripping down. The rev counter behavour indicates dirty connectors. Also ensure you have a Very sound Earth.
Believe it or not..the starter motor brush dust and low brushes here can lead you astray so take a look in this area.
No doubts we shall here more from you.
Crazy Frog has a good fault finding detail on his download page.
There are quite a few Guru's on here that will get your problems solved. Good luck Pal.
Ajays.

I see violet and white, green, black or yellow, but no grey on the wiring diagram. Ajays has beat me to it, I was going for the same switch. Brown is 'ground' or 'earth' in the rest of the Commonwealth.

Wiring diagram: http://www.bmwons.ca/K100/download/k100-Electrical.pdf

The vacuum switch had a violet/green wire and as club_c, I cannot locate a violet/grey. did you made a mistake and wanted to type violet/green?

As ajays said, the vacuum switch (as well as the altitude plug) were removed on the 1985 bikes.

You can check the
interactive diagrams or go to the download section of this forum where you will find all kind of information (including 2 full color electrical diagrams).

Bert

I have a clymer's manual that I'm working out of... seem there's some typo's in the drawings, some of the wires start out as V/gr (grey) and at the other end some will have V/g(green).

But the wire in question is definitely violet with a grey stripe on it. And it's on the opposite end of the location from the vacuum switch... it's the two wires that come out of the bigger conduit that the injector wires are in, furthest to the front, they go around the front throttle body towards the radiator, the brown wire is plugged onto a male blade connector, and that male blade connector is bolted to the rail that runs for and aft that is on the back side of the throttle bodies. The violet/grey wire is just hanging out there unattached. Now I'm really getting sort of confused.

Now my clymers manual shows a violet/grey wire going to the vacuum switch... for the early 1985 k1oort.

Thanks Ajay, I had started to post a reply to your first response to me, then Charlie wanted me to help him take the cowling off from his airplane... by the time I got back and finished my post it vanished into cyber muck when I had to relog in.

Dip switch, vaccum switch?????????????? will keep looking, thanks

I looked at those interactive schematics last night until I was blue in the face... was comparing them to the clymers manual. The clymers manual does show some Violet/grey wires, but I noticed the interactive drawings didn't show any V/grey wires on any of the locations that the clymers manual shows.

I think Ajay is right about one thing in particular... think I'm looking for something that's not there, but I sure would like to know for sure before buttoning up the breather assembly. I noticed on the top of the engine today that there was a number 84 on top of the engine block, in the area where the air box is, had the box and flow meter out of there today so I could get a good look in there to make sure there wasn't a plug for that violet/grey wire... even looked up under the frame just above that area.
The weird thing is the chewed up wire I cut off from the ends of both those wires was about 2"-3", and just trying to get the violet/grey wire to anything for a connection would have been very difficult, unless there was something bolted to the rail that the brown wire is fastened to. I haven't checked the violet/grey wire yet to see if it has voltage on it after startup, not sure if that would tell me anything. thanks bob

As for the fuel and temperature light they do not come on with the ignition.
Useful eh?

Regards,

Phil

which should come on in position "2": 1=engine oil pressure(red)
2=battery charge (red)
3=cold start/choke (orange) if control is operated
4=rear light monitor (red)
5=neutral (gearbox)/idle (green)
6= Less than approximately 7 liters of fuel in tank (orange)
7=Less than approx. 4 liters in fuel tank (red)

This is what my owners manual says in regards to telltale warning lights... pretty useful? so which is it?
But thanks Phil on the temp light... after re-reading owners manual I did see that temp light doesn't telltale, thanks.
1985 R100RT

Actually all of the above should light but the fuel lights are a bit "iffy" in I have heard they work on temperature but if the tank capacities are as stated either one or the other will come on but not necessarily straight away.
When riding they will go on or off depending on uphill or down dale so more a rough guide.
Brake warning light will go off after both brakes are activated but I disconnected mine as it was too unreliable and too much of a pain for a couple of globes.
From my point of view so long as oil pressure and alternator lights are on and then go off once started that is all I worry about.

Regards,

Phil

I will be taking the speedo/tach apart when I get the time, have to check the tach connections at coil first for corrosion. The tach sticks at 3200rpm but drops back down when the enging slows down, figure it's like Ajay said a bad connection. I looked the tech info over on here to see how to clean the contacts, seems like a fairly easy fix, will check the bulbs in there then. Must have a low fuel indicator of some sort to keep from getting stranded along the road sometime. Because of the unreliability of these low fuel lights, is there any alternative for low fuel indicators besides looking into the fuel cap while going down the road, or setting trip meter for a indicator ?

I saw one tech article where the writer used potentiometers, spelled that wrong I think, to measure fuel level. Thanks, bob

I find with mine the lights + tripmeter work well enough and the other theory is not to let the tank get too low anyway as it acts as cooling for the fuel and fuel pump.

Basically you have a 22 liter tank you can't use all of anyway.

The other alternative is the later bikes use a float type sender and therefore a gauge is possible although I think they just went with one light.

Where is that reserve switch when you need it.... of course then it would have been like the R-series and had one on each side of the tank which was really useful, not.

Regards,

Phil

I don't know Phil, about not using all the fuel, I mean I usually depend on the reserve lever to tell me when it's time to fuel. Like on a trip to Sturgis or such. When I put the new fuel pump in it I put a bit of gas in it (avgas) to get her a little cleaned out, and I turned the switch on to see if the low fuel light came on, it didn't, but may have put more than the first light amout in it.

I may just have to pump the tank out to see for sure if the lights work. The only thing I don't like about BMW is all the gizmos that they put on the modern bikes. I bought a toyota 4x4 a few weeks ago, 1990 model, one owner with 85,000 miles... it's has crank windows, no cruise. i sort of like the less is more thing.
I like this K bike but the electrical aspects seem sort of daunting to me, recon I'll just ride it and see how she works out.

thanks,bob

Don't worry we are here as a backstop for you, they are a great bike to ride and own.
Regards,
K-BIKE

Actually Bob I am right on the same wavelength as you and while I have grown to appreciate the K which probably has a bit to do with the badge on the tank something simpler would fit me better.

I keep saying it we just need a stable of different bikes for different occasions.

As for the fuel I could regularly do 300 k's non stop on my R100RT but about 200k's on the K100 sees the 4 litre light start to come on and the seat is pretty awful so I need a break then anyway.

Regards,

Phil

In stead of emptying your tank, just push the float of the level switch down and see at which point the light is working.
I re-adjusted mine (bent the rod) and now my 7 liters light comes on after 200km.

I'll take a look in the tank at the float you mentioned and see if I can activate it, good advice.

Still tinkering with the K before I go to work 2p-10p. I rode into town this mornig, 30F temps, got the title changed over, new plates. Then went to fastenal to try and find the 5mm screws I need for the windshield, currently it has ss finish washers with oval head countersunk screws. Half of them were missing, and I think the washers are not what is suppose to be on there... fastenal didn't have the right screws, so then on to Holt BMW and a talk with Marvin, he had black plastic washers that were suppose to be for it, but they had tabs on the mating side and a tab to catch the edge of the windshield, not correct either?. I have some slightly smaller aircraft type washers on there now until I find the right fasteners.

Also picked up some 7.5 weight fork oil to put in front end, got some rubber nipples to go on the throttle bodies to replace the dry rotted ones that were on their.

Also talked with Kent Holt (owner) while there and he shared a lot of good info with me on this bike related to the speedo change. Turns out this bike has around 33.000 miles on it instead of the 17k that the po led me to believe, he may or may not of known the actual mileage, although the speedo change notations were in the service book. Regardless I still consider 33k very low for a 25 year old BMW.

I did give only 1300 usd for it and it seems like a really solid machine. Splines will be the first major work I do on it, deciding when to do it seems the only issue, another rainy day perhaps. Thaks, Bob