Being new to K bikes and not knowing the history of mine, I've been systematically working my way through the "So you've just bought a K bike" page.
There are a couple of issues that I'm trying to deal with. I'm not sure what a K100 should handle like, but I reckon it should be better than it currently is. I picked up from a recent thread that my shock absorber has been installed upside down. I've removed it to send away for a rebuild.

Another issue is there is a small oil leak around the back of the gearbox and down the centre stand legs. As I was dismantling the back end, I wanted to see if I could find where the leak's coming from. While in the process of removing the final drive, I peeled the rubber boot back and around 100ml of oil ran out.
I checked the oil in the rear drive and there's still 250ml in there; the same amount that I put in two weeks ago. So the oil must be coming from the gearbox. Is it a difficult job to repair?

The rear splines appear to be in reasonable condition, but there was no sign of grease on them. I presume they've been washed clean by oil.

Puting a new seal in the rear of the gearbox is not a difficult job unless you want to do the bearings at the same time and I would not do them at less than 100000km.
On another note would you put your country in your profile it is a condition of being here. your info maybe a casuality of a glitch that cause some data loss a while ago and its a good idea to put the model and year of your bike/s in your signature that way we all know when answering any questions and you dont have to type it in all the time

On the handling issue the rear shock is important but also the front forks have you attended to them as we often see here oil that comes out looking like water and the smell is bad we are glad the forum doesn't do smells.
I have been through a few Ks myself and work on others and the best thing to do when you grt one is get right down to the nitty gritty and get personal and get to know it. More often than not it has been sold because the previous owner thought it wasn't worth doing the work or spending the money. So there is always work to do to get it up to scratch.

In my view I can see my location and signature, so it must be a glitch. I went back and updated my profile, so hopefully that fixes it.
Regarding the handling, the front end doesn't feel too bad. I've changed the fork oil and the old oil looked okay, not watery. I adjusted the tyre pressures and the handling improved slightly, but if anything accentuated the problem with the rear. It just feels vague, and tends to wander on corners. It gives me no confidence. I can't tell if its going to step out or not.
My bike has done 100,000 km.

You'll have to pull the swingarm out to see the gearbox seal so check the swingarm bearings. One of them on mine could be moved in all directions with a finger and it was like riding wet spaghetti before I started to strip it down. And there should be a date embossed on the tyres, my front is 2006 vintage

Getting the front up to scratch will make a bad shock more noticable and as Robin says the swing arm bearings and if the final drive bearings have any play the rear wheel tends to want to change direction slightly.
The bit with location was a glitch and heaps of members lost their profiles, all I had left was my name.

RobinW wrote:You'll have to pull the swingarm out to see the gearbox seal so check the swingarm bearings. One of them on mine could be moved in all directions with a finger and it was like riding wet spaghetti before I started to strip it down. And there should be a date embossed on the tyres, my front is 2006 vintage

Before you remove the swingarm see if it has any lateral (side to side) movement. There shouldn't be any.

I checked the swingarm bearings and they appear to be good.  I found no play or lateral movement, so I decided to stick to the shock absorber rebuild plan and see what difference that makes to the handling.
Meanwhile, I removed the swingarm and gearbox.  The gearbox was a little reluctant to remove, and it seems like it hasn't been out for at least ten years, if ever.  The splines were dry and rusty.  The clutch splines were showing distinct signs of wear, so I removed the clutch assembly.  The friction plate thickness measured 4.6mm  The manual says the wear limit is 4.5mm so time for a new clutch.
The splines on the gearbox input shaft show some wear, but they still look okay.  I'd certainly felt that the gear shift was pretty clunky, when riding the bike.  So I'm hoping that a new clutch and a fresh application of grease will fix it.
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The spline was very dry.  The slight oily smear you can see in the photo, only came off my finger when I touched it after removing the gearbox.

The clutch splines are cactus alright but the shaft splines are supprisingly good considering the state of the clutch. The shaft splines usually wear more at the gearbox end of the spline but they still appear parallel so should be OK to use.

Thanks for the feedback Rick.  You know, until very recently, I was a complete novice on BMW motorcycles.  These resources didn't exist in my old dirt biking days.
I read that there is a method to replace the gearbox output seal, without opening the gearbox.  I've decided to only replace the output seal and clutch, and then see how the gearbox operates.  Just taking a steady, steady approach, but building confidence in the process.  I'll order some new parts today, and post an update some time after they turn up.
Besides, I tend to only work on the bike at weekends.  Have to fit my hobby around work and family responsibilities.

Not sure if you know but most of us Aussies on here get our parts from Motobins in UK and it usually only takes about 2 days longer than from Munich Motorcycles in Perth which is as cheap as you get in Oz
http://www.motobins.co.uk/

Yeah, I had picked up that it is more cost-effective to order parts from the UK, thanks Rick.
It's Monday morning in England and they'll all be waking up in just a few hours time.

Hi everyone,

After a long wait for parts to arrive from the other side of the globe, I finished working on my bike, only to find . . . I haven’t finished.

I changed the clutch, seals on the gearbox input and output shafts and the rear of the engine, and a few other items that were needed.  I carefully put everything back together, lubed and torqued everything.

So I got the bike back on the road, and it’s working pretty well.  The thing that I was most anxious to try, was whether the handling had improved with the rebuilt shock (fitted the right way up this time).

The answer is yes, it is now a lot better.  It is far more willing to tip into corners than it was previously.  Surprisingly, I also noticed that the paralever rear behaves quite differently.  It is a lot more absorbent over bumps now.  I have a theory, to which I would welcome any feedback.

When I was reassembling the rear drive, I found that both paralever pivot bearings were notchy and wouldn’t rotate smoothly.  I reckon they’ve been damaged by overtightening.  These will obviously need to be replaced, but because I didn’t have any replacements on hand, I wanted to continue anyway.

Is it possible that the handling was crap, because the paralever pivots had been overtightened, to the extent that they were binding as the suspension moved up and down?  I was careful to tighten them so that there was as smooth an action as I could get, with no sideplay.  It’s not perfect.  There is a harshness that I can feel on small sharp bumps, that wasn’t there before, and I feel is due to notchiness in the action of the bearings.

However, I think I have a better idea of how a K100 is meant to handle.  Comparing before and after, it seems as though previously the back was trying to push the bike on in a straight line and it just didn’t feel like it wanted to turn.  Now that the paralever pivot is working better, the rear suspension geometry has improved, and feels more compliant.

More success another K back on the road.
I found that when the drive to swinging arm bearing was a bit rough things improved a lot when it was renewed, the bikes manners inproved markedly.

good work ....
yes indeed those pivot bearings do have a remarkable effect on handling

maybe not in the low 100s kph but up higher that little bit of slop translates to big dramas ...take it easy till you get it fixed .
good luck !!