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Very Hot Topic (More than 25 Replies) K100 Front end rebuild (Read 1189 times)
Semper Gumby
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Re: K100 Front end rebuild
Reply #15 - 06/13/18 at 09:13:57
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Here is cutaway plate and new position of brake switch.
  

Bill Gould †1980/03 R65 When at first you don't succeed....Moo!
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Semper Gumby
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Re: K100 Front end rebuild
Reply #16 - 06/13/18 at 09:17:32
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The mechanic who did the install drilled the new holes and use about 4washers to space the plate away from the triple tree.
  

Bill Gould †1980/03 R65 When at first you don't succeed....Moo!
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Tony Smith
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Re: K100 Front end rebuild
Reply #17 - 06/13/18 at 15:28:36
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Thanks for that. I seriously considered doing exactly what you have done, but I decided against it as I want to retain the ability to return the bike to standard should I ever want to - besides then I'd have to figure out an alternate mount for the blinkers.

Now worries re the plate, I've got no further than buying some alloy box section to make them from anyway. Nothing like leaving stuff to the last minutes,  this all needs to be done by 9 days time..

One question you are in a position to answer for me  is that of steering lock. I have a concern that the bars will hit the tank and I will need to restrict lock - if need be I intended to do that by the same method BMW restricted the lock on the R100 - drill the stops on the lower triple clamp and fit some 5 or 6mm bolts with reduced height heads. But I see you haven't done that, may I assume there were no problems with the steering lock?

The only other observation I would make on your install is to ask why you didn't use the  K100 method of routing the brake lines. When I realized how they had done it - from the master cylinder to the centre of the triple clamp axle, then down the axle and a simple "y" adaptor at the bottom going direct tot he calipers I found myself wondering why they were all not done that way - neat, out of the way and unlikely to chaff or catch on anything. Mind you it did help that I firstly got the pipe work that goes up the axle and that secondly at the time Motobins were having a special on the three stainless steel braided hoses required.

  

1978 R100RS| 1984 R65 | 1984 XT350 | 1992 KLE500 | 2002 R1150GSA
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Semper Gumby
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Re: K100 Front end rebuild
Reply #18 - 06/13/18 at 21:35:54
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Thanks Tony.† Boxworks did the original install.† For some reason they did the brake lines that way.† Iím assuming they did it that way for a reason.† Nathan is not one to suffer fools or foolish engineers well.† Perhaps the simpler system is difficult to properly service?† Btw - One of the brake lines is too long and I need to change it out for one the right length.

Steering stop -

Take a good look at the bottom of the steering head in the pics above (sorry about the funky aspect ratio). Boxerworks welded a 5/8Ē wide steering stop that sticks out at the bottom of the steering head.† This is the way itís done on the K100.  I asked them to do the same on my R65.  If you donít do this (or something like it) the forks will contact the tank.

Good luck. And watching your posts with interest.† Cool
  

Bill Gould †1980/03 R65 When at first you don't succeed....Moo!
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Tony Smith
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Re: K100 Front end rebuild
Reply #19 - 06/14/18 at 15:43:21
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Semper Gumby wrote on 06/13/18 at 21:35:54:
T
Take a good look at the bottom of the steering head in the pics above (sorry about the funky aspect ratio). Boxerworks welded a 5/8Ē wide steering stop that sticks out at the bottom of the steering head.† This is the way itís done on the K100.† I asked them to do the same on my R65.† If you donít do this (or something like it) the forks will contact the tank.



Thanks for that, I'm a little embarrassed as i actually own a couple of K100s that are in the restoration queue, but in my defence they are stored offsite. Still I should have simply gone and looked - that is a very simple and effective steering stop and would not even have to be ground off to refit the original forks I suspect. I keep telling myself that it will all go easily once I start, but I also remember the maxim "no project plan survives the first application of spanners". I don't want to be left half done and have to do a 400km ride on the KLE, but I'd have to endure that pain to avoid the humiliation two years running turning up on a modern bike.
  

1978 R100RS| 1984 R65 | 1984 XT350 | 1992 KLE500 | 2002 R1150GSA
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Justin B.
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Re: K100 Front end rebuild
Reply #20 - 06/14/18 at 23:10:24
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I didn't want to sacrifice a good headlight bracket when fairing the wife's bike so I tracked one of the instrument mounts used on the cop models...
  

r65_inst_bracket2.jpg ( 95 KB | 10 Downloads )
r65_inst_bracket2.jpg

Justin B.

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Tony Smith
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Re: K100 Front end rebuild
Reply #21 - 06/15/18 at 04:13:36
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Justin B. wrote on 06/14/18 at 23:10:24:
I didn't want to sacrifice a good headlight bracket when fairing the wife's bike so I tracked one of the instrument mounts used on the cop models...


I considered one of those too. But I am not destroying the stock mount, merely drilling four holes into it. Smiley
  

1978 R100RS| 1984 R65 | 1984 XT350 | 1992 KLE500 | 2002 R1150GSA
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Semper Gumby
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Re: K100 Front end rebuild
Reply #22 - 06/15/18 at 13:05:17
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Oooh.† Justin what is the part number on that bag?

TIA.† †Roll Eyes

Oh and thanks Justin.† I just identified the last part of the pichler fairing install.† I though it was something that goes on top of the speedo mount.† But now I think it is the Pichler speedo mount.† It may be surplus to me now.

Off topic.† But does anybody know the difference between K100 forks and K75 forks.† On the surface they look the same but I suspect the diameters are slightly different.† Is it 41mm vs 41.3mm?† Inquiring minds musts knows....† †Shocked
  

Bill Gould †1980/03 R65 When at first you don't succeed....Moo!
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Justin B.
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Re: K100 Front end rebuild
Reply #23 - 06/15/18 at 13:31:38
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I don't know if I still have it but I'll check.  I ordered several of these, probably 10 years ago, and at that time there were 12 left worldwide.

I may have one left but I'd have to check.
  

Justin B.

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Burt
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Re: K100 Front end rebuild
Reply #24 - 06/16/18 at 07:19:09
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Bill,†

This should point you in the right direction for your fork query.† http://www.k100-forum.com/t6919-k75-forks† Post 2 provides a table.† A very useful and friendly forum and yes I am a member.†

There are two different K75 fork diameters (41 and 41.3mm) and further into the forum you will find there are different volumes for different K bike forks.†

As a general rule the K75 forks are preferred over the K100s and as a result are a bit harder to find.†

Oh, and I own a few K75s.† It is a medical condition known as K pox.†

Cheers, Dave.
  

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Tony Smith
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Re: K100 Front end rebuild
Reply #25 - 06/17/18 at 00:54:53
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Burt wrote on 06/16/18 at 07:19:09:
Oh, and I own a few K75s.† It is a medical condition known as K pox.†



Dave, I think I may also have a case of K-pox, I already own two K100RS bikes, one of which was in running order when I bought it, in fact my Younger brother rode it 1,000 odd KM to where I was supposed to pick it up a week of so after he left it. Sadly that didn't happen so by the time I did get it home on a truck, it was a non-runner. A pity because I wanted to use its electrics and engine to get my other one running, it is a beauty as it was parked up under hessian bags when it was only a few months old in the late 80s and there it sat untilthe parents of the owner began to make preparations to go to a retirement home. It looks immaculate, sadly though the rats got into the wiring and nested above the engine causing an amazing amount of damage, hence my intention to do an engine swap.

Today I have accepted custody of another non-runner, this one has been in the hands of someone I know for nearly 10 years, it has an interesting fault - connect a battery and turn on the ignition and it blows the hall effect transistors to smithereens. Over the years he has had a number of attempts to correct this, including the most recent one yesterday. He rang me to say "take this piece of $hit away please".

So yes, I think I have K-pox.


Which brings me to the point of this post.

My Haynes manual only covers the models 1983~1987 and I do note it is probably brimming with Mr Haynes' usual typos, inaccuracies and other nonsense (more on this in the next post).

According to my manual K75 and K100 forks have the following metrics:-

Travel
K75S and any model with "S" suspension - 135mm
All other models - 185mm

Stanchion OD - 41.325 ~ 41.350mm
Lower Leg ID - 41.400 ~ 41.439mm

Fork Oil capacity

K75S and any other model with "S" suspension - 280cc
K100 and all other K75 models  - 330cc
K100RS/RT/LT - 360cc

Recommended fork fluid

A bloody long list which includes the following fluids that I know the characteristics of - BP Aero Hydraulic, Shell Aero Fluid 4, Spectro SAE10 (for competition use only supposedly).

Given that these things are so very similar to R65 forks internally I am goign to start with a 50/50 mix of Castrol Fork 5 and Fork 10, I will be very surprised if that isn't in the ball park. For someone who weighs less than my 130kg I'd start with 100% Fork 5 and see if that suits.


And lastly.
I changed the wheel bearings and wasn't that a revelation. After years of performing strange acts and mouthing incantations to change airhead wheel bearings, the K-bike front bearings were a revelation.

Sealed ball bearings with an internal spacer. It took me all of ten minutes to change both bearings (luckily I own a set of expanding blind bearing pullers). So quick and simple I found myself in disbelief that BMW would stoop to doing something the easy way.

Yes, they will not last the moon-and-back-several-times distances that the Airhead wheel bearings last, but 10 minutes too swap out bearings is hard to beat.

Of course Mr Haynes made note of the fact that you are supposed to heat the wheel before basing bearings out or in. I decided to give them a love-tap and see what happened before putting on the thinking cap to work out how to uniformly heat something of that size to 100 degrees centigrade. Fortunately both bearings came out easily and there was no damage to bearing bores. I do know about the requirement to heat early airhead hubs, but this is a far more massive casting.

So, got to look at a friend's bike that is making funny noises and if I get home early enough, I might assemble the K-100 forks.



  

1978 R100RS| 1984 R65 | 1984 XT350 | 1992 KLE500 | 2002 R1150GSA
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Burt
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Re: K100 Front end rebuild
Reply #26 - 06/17/18 at 06:20:57
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Quite a mild case there Tony but the symptoms are evident.

The K100 8 valve began to be replaced by the 16V from about 1991 but the fork oil quantities are correct.† The only one not listed is for the K75RT with Showa forks which had a capacity of 410cc.† One of my Haynes manuals is to 1993 and the other covers the whole 75/100 range.†

I was near the Haynes Museum in Somerset only last Tuesday.† If I had known I could have popped in and picked up a new manual for you.†

In fact if you want some advice on fork oils there is a(nother) thread right now.† http://www.k100-forum.com/t13632-woohoo-another-oil-thread-fork-oil#163980† 7.5W appears to suffice.† Although we are talking about a nearly 50kg weight difference between K100RS and R65.

From what I have seen with wheel bearings, the only ones which are a pain are the K75 3 spoke wheels which uses two different sizes on the front wheel and one of them is $60+ !† I also found it easier to replace steering head bearings on a K compared to the R65.†

A long time ago when I did some serious touring on my R65 I was in the habit of carrying spare wheel bearings with me and one lonely Sunday afternoon in the middle of the Victorian countryside I realised I had a stuffed front wheel bearing.† So pulling up in the middle of nowhere I spied a farmer on his tractor and explained my predicament.† Come with me then as I rode to his shed where he just happened to have a BFO lathe.† So we turned down the axle and I whipped out a set of bearings and was on my way again.† Talk about luck.†

Quick Nurse, before we lose him......†
  

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Tony Smith
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Re: K100 Front end rebuild
Reply #27 - 06/17/18 at 16:07:00
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Burt wrote on 06/17/18 at 06:20:57:
Come with me then as I rode to his shed where he just happened to have a BFO lathe.† So we turned down the axle and I whipped out a set of bearings and was on my way again.† Talk about luck.†



Everyone is entitled to some luck from time to time Smiley

I would not be able to work up too much interest in the Showa forks as I do not approve of the way Showa put their forks together.

Firstly they use inner and out bushes that the leg slide on. At first blush this might seem to be a good idea as it allows replacement of the wearing part. BUT, I've never heard of anyone who actually managed to wear a "traditional" fork leg out to the point where it required replacement, whereas Showa bushes require replacement every seal change (and in fact I have some empirical evidence that suggests that wear on the bushes in fact causes the seal to fail).

Showa forks require seal drivers and a turned up ring to add to the seal driver to fit the lower bush - once a showa fork is assembled the only way to take it apart is to use violent downward motion of the leg (with or without added weights) with the damper rod retaining bolt released to drive out the outer bush - if this works, it destroys the outer bush and you get to buy a new one.

It is possible for the inner bush to become partially dislodged during this process making it impossible to remove the leg, if this happens you get to put a hacksaw through the leg so that you can remove the bush and fit a new one, along with the new leg you just had to buy. The is an expletive ridden video on Youtube of Chris Harris discovering this awful truth.

I have some form with Showa forks, it turns out that the KLE has a very near cousin of the forks fitted to late K, F & G series BMWs.


Suffice it to say:-

Showa forks - not a fan!



  

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Julio A.
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Re: K100 Front end rebuild
Reply #28 - 07/28/18 at 04:39:00
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Curious. Can a snowflake be adapted to the K100 front end?
  

Julio Alarcon
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Tony Smith
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Re: K100 Front end rebuild
Reply #29 - 07/28/18 at 17:03:27
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Julio A. wrote on 07/28/18 at 04:39:00:
Curious. Can a snowflake be adapted to the K100 front end?


Quite probably, you would have to make up reducing sleeves axle mounts in the front forks, then turn up a axle that would "lodge" securely in one fork leg, then reduce in diameter (the same way the standard one does) to provide, along with a turned up sleeve at the other end, to preload the bearings, and centre the wheel between the forks.

Then you would have to machine up new spacing kits to centre the brake calipers (whichever ones you decided to use) over the discs.

So, the answer is that yes you could, with an awful lot of engineering.

my question to you would be "why would you?"
  

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