Greetings fellow brick lovers.

I recently picked up a lighting used (35.5k) 1991 BMW K100RS.  I think I paid a decent price, but it didn't have panniers and the more I ride it the more I realize it needs some TLC.

Front Brakes are WEAK.  I purchase pads, but when I started to do the maintenance, I realized the hoses were spongey (if that's a word) and it's in bad need of some suspension work.  The rear shock is nothing more than a screen door slammer and the front is...bad.  I purchased fork seals and cups (as one was leaking) and am going to RnR those and verify the proper cc of oil is in each.

The ABS light is on and I don't really want to go to the expense of fixing that.  I know I need to ask for a password from a moderator.  I'll figure that out next.

Just wanted to say hello, so I can start being a active member

Kevin (aka HellFishTat)
Raleigh, NC

Hi 
Glad to have you here. 
You came to the right place for info.
 They know everthing about the K-bikes here.

Welcome to the site.

You are in the right place.

Have a look at the section You have just bought a K Bike. One you have 3 posts in here you should set up a thread and we will add our bit. Also get your hands on a Clymer manual. Everything you need is here but its hard to beat the manual too.

It looks like some TLC needed but that's often the case with low mileage bikes especially if they have been off the road.

The spongy brake pipes cause weak braking. New steel braided pipes will cure that. The spongy feeling is a normal sign of deterioration but must be fixed. K brakes when they are right are really good. You should do all the hoses but the ABS system means it needs to be done carefully and you need a power bleeder. there should be a section on it here too.

Panniers and Z frames can be got off eBay or someone here might have a set.

I suspect a spline lube and check of seals is on the cards too.

ABS advice here too, needs expertise but some remove the ABS rather than spend money to fix it. The brakes will work fine. However if you are determined it is worth exploring as there are a few items like wheel sensors and more that are cheap. The biggest issue is dodgy electrical connections because of age and this too can affect the ABS system so you need to carefully deal with that. Even without a wiring manual you can do it if you simply open one joint at a time and deal with it before going on to the next. This is a tedious but cheap exercise needing some Deoxit and patience. It is a great way of getting to know the bike too.

There are a few other things too. Fuel hoses perish, replace them. If brake lines are bad chances are these will be perished as well. Use only the BMW ones, they are cheap but its a tank and top half airbox off to do it- you will have tank off to do electrics anyway, battery out too [easy] gives you much more room. Also do the coolant pipe from the radiator to the overflow, its cheap but perishes too. Same with the sightglass pipe on the side of the coolant bottle, again an easy fix. If the battery is out you will see two allen bolts on the left side which hold down the starter motor. It too comes out [give the bolts WD40 first] easily and worth cleaning it inside. With the low miles the brushes should be fine but cleaning improves electrical performance.
 
Get your 3 posts up and start a thread, we will all add our bit The bike needs tlc so don't use without fuel filter change and get rid of the gasoline in the tank. Ethanol in the gas causes problems but replacing the filter and a few other bits inside will save some frustration.

A word of warning, make sure the battery is good and known to be good. A bad battery can fry the starter relay and cause a lot of other problems and false readings. This is first on the list before doing anything.

I hope it doesn't all sound a lot. I got an 84RT some weeks back and did a lot in 3 days. I had issues like stripping and painting stands and part of the frame, changing heat shield and more. I still have some jobs to do like the fork seals, head bearings and will also change brake lines.
 
The thing I found is there will always be someone around to help you with things. There can be fun when two or more get together for a workshop session to tackle jobs that need extra expertise or manpower and do 2 or 3 bikes. Just make sure you have the right supply of parts and you will get that advice here too.

Best of luck with it.

Kevin,

New here too, but not new to K bikes.

How good is your battery? These bike's ABS systems do not like low voltage.

Have you tried the reset procedure?

On my former '93 K-RS I could not get the ABS to reset. Placed black tape over the annoying light show. Couple months later I just happened to look under the tape and the system had reset itself.

Once you get it operating normally, these systems (especially ABS I, which was used until the end of '93) are pretty stable and most are maintenance free.

But make sure your battery has good voltage.

John

John,

Well put. Important Kevin is not scared off, the Ks just seem so simple when you get to know your way around them.

92KK

I have been working my way down the list on Ted's House.  I need to run to CapitolBMW this morning and get fork crush washers as I forgot them last week.

I looked at getting a set of spiegler SS brake lines, but $240 for the front only!  The whole kit for my '99 R1100s was only $200.  This ABS 1 is looking more and more like it's going to be sitting on a shelf.

I love wrenching on old bikes, so don't worry about "scaring me off".  I'm 50, and that helps keeps me out of the bars.  I can't believe i wrote that with a straight face.

I'd like to undertake the spline lube on boths ends of the shaft asap.  We're about to get into the best riding season here in the Northern Hemisphere and I don't want to be out worrying about something happening.

Has anyone documented this procedure here?  I'm sure they have.  Let me use the search button.

Kevin (aka HellFishTat)
Raleigh, NC

Don't be put off by the ABS, chances are quite high it is a simple matter and ABS1 is supposed to be good.

You have to do the brake lines and brake fluid change anyway, but I was with someone recently and he had got some good brake lines over here from UK for £100 equivalent of about $150 or so for an ABS K. 

If the battery is off form it can cause a fault warning as mentioned by John. The thing to realise is the electrics are sensitive to battery voltage just like any modern car, the K was ahead of its time.

 

Hi Kevin,

Welcome to the forum as mentioned the guys on here know the K 's inside out and beleive me this forum is as good as any manual and the banter is good with some great folk enjoy.

BIG D

I love wrenching on old bikes, so don't worry about "scaring me off".  I'm 50, and that helps keeps me out of the bars.  I can't believe i wrote that with a straight face.

We love wrenching on old bikes too, Ks respond well to 'old guys wrenching on them'. This led to plenty of banter over here in Ireland and a bunch of 'more mature' gentlemen making a trip last weekend to Bushmills distillery in Antrim. Check out Irish Eccentrics.

On a serious note the K is a lovely bike to work on, with the skills you have those jobs will be done well. With them done you have a bike that's good for another 10 or 20 years. Its easy to go through the entire list so it needs little work afterwards. The K was made with this in mind because it has a cup holder for serious work.......the flat cover of the under seat tool tray.

People here swap and sell off parts. It's not a commercial site but is used for disposing of unwanted parts. I sold off a fan for my LT, also just sold a spare tyre, bought one or two more bits and it works out good value and of course it makes friends.

Members here have found most of the legitimate short cuts and quick was of doing jobs and this is invaluable. Post a problem and someone will have the solution or a part to solve it.

After a bit of experimenting I found that the front forks perform best with the correct amount of 15 weight oil, otherwise there is a bit too much travel especially under brakes.  When the Nivomat rear gave up I replaced it with an Australian built IKON which is excellent. 

Another thing to watch out for is the backlash in the final drive and you should be able to adjust it after removing the drive shaft to lube the splines.  One sloppy dealer service resulted in a highly worn final drive that had to be replaced.

Changing the brake hoses won't alter the braking efficiency very much. The limiting factor is the relatively puny master cylinder piston diameter. So don't be too disappointed when not much difference is apparent with new hoses.

MikeP wrote:Changing the brake hoses won't alter the braking efficiency very much. The limiting factor is the relatively puny master cylinder piston diameter. So don't be too disappointed when not much difference is apparent with new hoses.

I did forget about that master cylinder issue, but that depends on which one is on your K. I wrongly assumed you might have the bigger one, if not then is a change needed. Either way though I would change hoses of they are original.

92KK K100LT 193214 wrote:

MikeP wrote:Changing the brake hoses won't alter the braking efficiency very much. The limiting factor is the relatively puny master cylinder piston diameter. So don't be too disappointed when not much difference is apparent with new hoses.

I did forget about that master cylinder issue, but that depends on which one is on your K. I wrongly assumed you might have the bigger one, if not then is a change needed. Either way though I would change hoses of they are original.

a bigger one?  have you been speaking to the mrs?  seriously, what "issues" are syou referring to?  may be I should have bought the R1200s I've lusted over for years

The issue is that the K100 & K75 was fitted with a (relatively) small diameter piston in the front master cylinder. From the K1 & K100RS 16v onwards a much bigger piston was fitted (20mm versus 13mm IIRC).

The brakes are fine. It's just that they need a bit more effort at the lever than many people are used to these days. It's understandable that people believe the hoses are expanding under pressure, explaining the effort required but it's really just a matter of the pressure being generated by your hand and not a huge piston.

The simplest fix is to ride something like an R80/7 with ATE calipers and the cable-operated master cylinder under the fuel tank. Believe me, after that you'll believe that your K100 has too much stopping power. 

My '92 has adequate brakes- 2 fingers to stop quickly.

Kevin's should be the same if it is the same master cylinder that it left the factory with. '90 through '92 had the same brakes as the K1100RS.

The question is how does the OP define "a 1991" bike? I own a bike built in 1989 and not registered until 1992. 

In the UK we tend to refer to the age of a bike as the year that it was first registered for the road. I know that it varies in other parts of the world.

MikeP wrote:The question is how does the OP define "a 1991" bike? I own a bike built in 1989 and not registered until 1992. 

In the UK we tend to refer to the age of a bike as the year that it was first registered for the road. I know that it varies in other parts of the world.

Easy, a '91 should be a 16 valve with 3 spoke wheels.

The attached Vehicle Identification Number plate has the date of manufacture

And the K100RS4V is easy to spot- exposed engine like the earlier K100 but 16 valve engine and 2 piston brake calipers like the K1100RS

(to add to what Bikerboy wrote)

sugarhillctd wrote:The attached Vehicle Identification Number plate has the date of manufacture

And the K100RS4V is easy to spot- exposed engine like the earlier K100 but 16 valve engine and 2 piston brake calipers like the K1100RS

(to add to what Bikerboy wrote)

Just to confuse even more my 92LT has no plates on the left like the photo, they are on the right hand side.

As CF said a long time back, we should post the chassis number to avoid the confusion.

The registration year is not a guarantee of the date. My RT has two numbers, an original and a restamped number, both marked as RT. It is legitimate but may be confusing for some parts as the original number is to be used for frame related items and the later number for most other things.

Each of us is probably right but we are maybe coming from different perspectives. Going back to my initial post 2 finger and even 1 finger on the front brake will stop me, even on the 84RT. It is by no means soft or in need of huge pressure. On closer inspection I now see the 84RT has the same master cylinder as the 92LT. I do know the RT had some brake work done by the last owner and this was possibly changed. The RT calipers are also the exact same as the LT, the RT forks are stamped Brembo.

Given the absence of history and the need to change fluids a caliper upgrade is not difficult. But post a photo so we can see, just in case there is another problem.

To confuse even more a friend of mine did a brake test on a dyno before and after a hose change [from poor and spongy rubber to metal braided pipes] and it did in fact make a big difference. If the pipes will swell at a lower pressure than is needed to stop the bike then they will limit the braking pressure of the pad on the disk/rotor.

1991 k100rs4v with brembo calipers up front.  I was lamenting spending the cash when my brother asked me, "did you RTFM?".

a quick look pointed out many things that could be a possibility.  
#1 = change the brake fluid
#2 = properly bleed the brakes (done by doing #1)
#3 = worn brakes (already have replacement pads, so that's next)
#4 = glazed pads (see above)
#5 = contaminated pads

I'll take care of all this next weekend when I do the fork seals.

For all our Australian members, I'm always searching for someone to ship (at my expense) some Bundy OP this way.

Kevin

If you are bleeding the brakes manually put a block between the lever and the bars to stop the lever coming back all the way. It prevents the master cylinder seals getting damaged on the inevitable wear ridge in the master cylinder that exists due to time and wear. Of course if a PO has done this it could affect braking performance.....

It sounds like you will have a great bike when the catch up jobs are done.

92KK K100LT 193214 wrote:Kevin

If you are bleeding the brakes manually put a block between the lever and the bars to stop the lever coming back all the way. It prevents the master cylinder seals getting damaged on the inevitable wear ridge in the master cylinder that exists due to time and wear. Of course if a PO has done this it could affect braking performance.....

It sounds like you will have a great bike when the catch up jobs are done.

I have a vacuum bleeder.  Actually my brother has a vacuum bleeder and a garage with a lift and all the pneumatic tools I could ever possibly need.  Decades ago I learned a valuable trick when working at his house, if you drop one if his wrench's more than twice, he say "give me the damn thing" and do most of it for you.  I bring beer.

Good to hear that on two fronts. In time the K is actually quite easy to work on but one needs to get to know it. Sounds like you have most of what you need. I think you could find a nice steady arrangement of a few days off to your brothers, beer under your arm, a few bike parts in your tank bag and a nice day ahead.

Do keep us posted because we have a good fun side to the site as well.

Olaf

92KK K100LT 193214 wrote:Good to hear that on two fronts. In time the K is actually quite easy to work on but one needs to get to know it. Sounds like you have most of what you need. I think you could find a nice steady arrangement of a few days off to your brothers, beer under your arm, a few bike parts in your tank bag and a nice day ahead.

Do keep us posted because we have a good fun side to the site as well.

Olaf

Thanks Olaf!  I will.  I was (still am kinda) active on the R1100s/R1200s forum.  Bidding my time waiting to find the perfect R1200s.  Love the boxer toque, and after 800 miles in the saddle, am really loving the brick.  I can't wait to get it sorted out and find out what the old girl can do.