'85 K100 Handling/Braking - Best Bang for Buck?

[Brad-Man]

A couple of weeks ago I bought my first BMW - an '85 K100 which of course I let everybody know in the Front Porch.

Before and after the purchase I have been gleaning info from a few forums - especially this one about what to expect and how to improve and set the bike up.

My current engine is fine, but always nice to have a spare, tranny MAY have 165K on it or more.  I KNOW the rear disk is a bit on the thin side so knew I would have to deal w/that, but otherwise the bike is running fine.  I don't know when the last spline lube was done for either the driveshaft or clutch, but the previous owner said he was having a bit of difficulty downshifting from 4th to 3rd and 3rd to 2nd.  I did not notice this when I drove it home.

I intend to use this as a daily commuter in town and on trips w/the 'Better Half'.

I have bought a '91 K100 4V engine and tranny w/40K on 'em along w/the final drive and drive shaft/fork w/brake disk and caliper for $400.

I am going to wind up doing something w/the front suspension/brakes and of course have to get a shock for the rear.

I figure if I go to do the spline lube and have problems, I can always replace the tranny-back and have the benefit of the Pararlever, of course having to pay for the shock - which I would wind up paying for even if I kept the current setup, so why not go ahead and convert?

Front fork-wise I am having some difficulty in deciding what to do.  A lot of people recommend just putting on the K1004V/K1100 front end, but I also hear that those are the Marzocchi forks and that I may be better off keeping the F&S forks and putting new springs and emulators in them.  Of course I have seen some enterprising people have put GSX/R front ends on theirs, which sounds great - inverted forks, better brakes/damping, but a pain to set up the damping/rebound on.

Brake-wise I'll go with SS lines and probably EBC Pads - Ceramic/Organic no matter what I do.  I can build adapter for 4 pot calipers.

I don't feel the need to go with the late K wheels just to get radials - I see Avon has a setup that will work - but I do have a concern.  Is the lip on the weels for Bias Ply tires diffferent that the lip for radials?  If so might this cause a problem?

I am no the boy racer-type any more, and when I want to feel that way I'll take out my '75 RD350 w/ported, squished and chambered RD400 engine and have a lot of fun in the curves.

What I DO want is a better handling, stopping and riding bike for daily use.

Opinions please - and thank you...

[frankenduck]

Does it have a one-piece front fender or does it have a 2-piece front fender with a fork brace?

Braking:

One option would be to replace the 2V 13mm master cylinder with a 4V 20mm master cylinder.  Probably won't give as much improvement as four pot calipers too but should help.

Instead of replacing the three brake lines with a kit, another option would be to run a metal line between the calipers and then run a universal (generic) braided stainless line from the master cylinder to the right caliper.

[frankenduck]

Rims shouldn't be an issue bias vs. radial.

[Brad-Man]

Duck:

Thanks for the info on the rims - load off my mind.

Asfar as the MC goes - that would make it HARDER to apply brakes and modulate them wouldn't it.

I know that a lot of RD guys drop from a 15mm MC to a 13mm and gain better brake feel/modulation.  More lever travel for the same pad movement.

What you seem to be suggesting counters that.

I know that I would have to go with that size if I were to put oon 4 pot calipers because I would need to move more fluid for a given amount of lever travel...

The solid line is to me a great idea connecting the 2 front calipers - I believe much better aesthetics...

[frankenduck]

Yes, I agree that going with a smaller MC would give you better leverage and more "feel." 

However, using a larger MC pushes more fluid for a given distance of piston travel.

And the actual lever to MC piston leverage between the two MCs is not identical.

I've never tried the larger MC with the 2 pot calipers but do plan to experiment with it in the near future. I think that's the only way to really tell if it makes the braking better or worse.

[frankenduck]

The part number for that metal line is 34321458402 - about $17 new.

[Brad-Man]

Good info.

What is your take on forks?

[mjydrafter]

Good info.

What is your take on forks?

I know Duck can answer this better than me, he has swapped in newer forks before.

What set up do you have?   Is it the one piece fender, or is it the 2 piece fender with fork brace.  (the red bike above of Ducks has the 2 piece)

The one piece looks like this:


I believe that the 1 piece was stock on the early K100's.

[frankenduck]

The nakeds and RTs had the one piece front fender.

The LTs and RSs has the 2 piece with a fork brace.

There was a company that put out an aftermarket fork brace called Telefix for the one piece fender bikes.

[Brad-Man]

I have an '85 so I have the one piece fender.

I'm thinking that I will install new springs and emulators on the F&S forks and have a better set up than the later forks - tho' perhaps not quite as stiff...

I'll get the fender brace too...

Unless you're saying that the K1100 forks are better...

[frankenduck]

The K1100 forks are better and what I have on my K75.  They come from the factory with progressively wound springs but they're a larger diameter so you have to replace the whole front end:

Fork trees
Forks
Axle
Wheel
Rotors
Calipers
Master cylinder

And then some other stuff to move the dash pad forward on the fork trees.

This isn't a big deal to me as I have a bunch of this stuff lying around. For somebody else and all of the expense and trouble involved I think you'd be much better off just selling the K100 and buying a K100RS4V or K1100.

[mjydrafter]

You could also upgrade to the braced forks/fender set up pretty reasonably with a little ebay-fu.  I upgraded mine, and I will have to do some research, but I don't think it was much more than ~$100.