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Old 11-24-2011, 08:22 AM   #1
bay OP
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bmw r100 fork swap

hi does anyone know what forks are a direct replacement for an r100 from 1978.i have the standard forks with ate brakes which are ok but i would like a little more stopping power.i guess the forks and front wheel from a mystic would fit.The bike is currently in cafe racer form so i would like to keep the spoke wheels.also does anyone know if a /6 tank will fit a /7 as i really like the style.many thanks
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Old 11-24-2011, 09:53 AM   #2
Wirespokes
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Welcome to the forum bay!

There are problems with installing spoke wheels on anything besides the 74-80 Ate front ends.

If you go with the 81-4 Brembo front end, you'll need to source the scarce police front wheel that was specifically made for those bikes.

The R100R uses a radically different wheel than what comes stock on the rear of your bike. With difficulty I believe your standard rim could be laced to the R100R hub. But that's just my guess.

Any one of the front ends will attach to your bike, but I'd suggest just getting the ATEs to work properly. They won't give you stoppies, but they can safely stop the bike.

A /6 tank will fit a /7, but it is shorter and will leave a gap of an inch or so between the tank and seat.
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Old 11-24-2011, 04:07 PM   #3
disston
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This is how I remember it. The /7 tank holds more gas, it is bigger. Therefore the /7 seat is shorter. That is the basics. To carry this a bit further. The /6 tank will fit with a /7 seat but leave a gap. The /7 tank will not fit but hit the /6 seat.

You can help the ATE brakes with semi-floating rotors. Rebuilding an old system helps.

I'm not giving up my spoke wheels, so I don't tailgate.

Charlie
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Old 11-25-2011, 10:27 AM   #4
bay OP
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bmw r100 fork swap

well today i fitted a handlebar mounted resovour and stainless brake lines,which all did away with the under tank system.bleeding the brakes was a sinch,so with fresh pads i went for a ride to scrub the new pads in and was very pleased with the result.so now i can keep the ate brakes and concentrate on makeing the forks work a little better.does anyone know of a good solution.ive read that the triple trees from an r65 helps and progressive springs,is this true .
please for give any spelling mistakes as english is not my first languge,thanks
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Old 11-25-2011, 02:04 PM   #5
Wirespokes
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Spelling boo boos forgiven!

Actually, you're doing a million times better than if I tried communicating in Danish! So well done for doing so well!

Glad you managed to improve the ATEs enough to leave them!

What is your complaint with the forks? What do you feel needs improved? What is the problem that needs fixed?

The reason I ask is because I don't have a problem with the top clamp and have different fork braces on some of the bikes and really can't tell that much difference between them and stock. Then again, I'm not riding over 75 or 80mph very often. Perhaps if I was travelling high speed and cornering on rough roads, I'd notice it. I do like to ride fast sometimes, but perhaps I've figured out how to handle these bikes and don't have problems with the front end.

So I'm curious what the problem is you're wanting to handle.
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Old 11-26-2011, 06:59 AM   #6
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bmw r100 fork swap

the reason i would like to improve the forks is they tend to dive alot under brakeing,even when the brakes were rubbish.ive tried new fork oil so i guess new springs is the only opption,and seeing as the bike is from 78 i suppose one can not expect to much from standard springs.can anyone recomend other fork springs.the triple trees are also on my list to change, i really dont like the idea of only one bolt per leg to keep them in place plus they have to be stiffer with a top yoke to hold them instead of just a hole to go through.I hope this doesnt sound like i think these bike are crap,because thats just not the case,i love the pull from the motor and as a cafe they really look cool.theres nothing like a bmw when you look down at that motor when youre riding,simply awsome.
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Old 11-26-2011, 03:37 PM   #7
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New springs and/or after market springs will help. BMW even has a heavy duty spring for your bike. The after market spring most heard about is from "Progressive". Then there are spacers that can be incorporated. There is cutting the springs, to make them stiffer. The weight of the oil; I think our bikes all had 4wt oil from the factory. Many riders use a heavier oil than that, 7.5 and 10 wt I've seen reference to. All this takes sorting out to figure what you want, how stiff, etc.

But watch out for something called "Anti-Dive Springs". I don't think they are even sold in the US of A any more but they could still be available if one was looking for them. They are short springs, about 4 inches long, that go on the bottom where the bottom bumper goes. Current logic is they don't work. I think that was also born of experience because a lot of riders had them and it's almost more common to find old forks with them than with out.

So I can't tell you what you will end up with. Pick one to start with, either 1) stock 2) heavy duty 3) progressive. I list the options in the order I believe is stiffer the higher the #. I guess you are a Progressive, I think, don't know why, maybe because you call your bike a "Cafe". They should be available in Holland or mail order. And get the lighter weight oil to start. Try 5 wt if you can find it. You can then change the oil to heavier if you want. Some people recommend using "Fork Oil" and not Transmission Fluid.

The most popular top brace these days is made by Toastertan. He is on this list and I'll try to find his info for you if I don't forget. It only has one bolt in the position I think you mention but contrary to what you think it works. These braces have been in short supply for a while but I think he might be getting ready to do some more soon. There are of course other options and some of them work but there are also some that are just decoration. Beings as I don't remember which is which I stick with what I know and that is that the one to get, if you can, is the Toastertan brace. It might be really cool for your bike if they are actually rare in Europe. But there might be things there that I don't know about either.

Here is an article that discusses problems these bikes have with forks not being in alignment. This may not apply to you but the article will teach you much about the machine.

http://w6rec.com/duane/bmw/fork/title.html

Charlie

ps; here's info on toastertan:

http://www.pbase.com/toastertan/top_braces
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Old 11-26-2011, 03:47 PM   #8
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Here is the most recent info from Toastertan. Still not sure how available these are yet. He does only do this as a side operation, i.e. he's not making money off this.

http://www.advrider.com/forums/showthread.php?t=741999

Charlie
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Old 11-26-2011, 04:26 PM   #9
Max Headroom
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Quote:
Originally Posted by Disston
*snip* But watch out for something called "Anti-Dive Springs". I don't think they are even sold in the US of A any more but they could still be available if one was looking for them. They are short springs, about 4 inches long, that go on the bottom where the bottom bumper goes. Current logic is they don't work. I think that was also born of experience because a lot of riders had them and it's almost more common to find old forks with them than with out.
I had a pair of anti-bottoming springs in my 90S and took them out when doing a fork seal replacement last year, because I doubted that they were doing much apart from making an annoying rattling sound at low speeds. I quickly put them back in after a few short rides, because the front forks bottomed out in their absence. Same bike, same rider, same roads, same riding style . . . . they are back in and staying in.

YMMV etc
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Old 11-26-2011, 04:33 PM   #10
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The San Jose, CC Products top brace so popular back in the /6/7 era are still available and did the job well on my /6 and is doing great on my current /7. When you hit a bump in a tight lean, it provides better line holding, less drift, just firmer control. It helps tame the rubber cow until your skills get StupidFast.
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Old 11-26-2011, 04:35 PM   #11
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bay,
I had exactly the same problems you describe on my 78 R80, under even mild braking the forks dived quite badly, not a big problem in a straight line but very unsettling when using a little brake coming up to, or into a corner.
I fitted progressive springs from Motorworks in the UK, for me it transformed the handling, I simply fitted them with no extra spacers or anything & found them a great improvement.
I lost a little of the softness of the standard springs but it's more than made up by the lack of dive & better handling.
Get some progressive springs, I don't think you'll be disappointed.
http://www.advrider.com/forums/showthread.php?t=583503
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Old 11-26-2011, 04:48 PM   #12
disston
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Quote:
Originally Posted by Max Headroom View Post
I had a pair of anti-bottoming springs in my 90S and took them out when doing a fork seal replacement last year, because I doubted that they were doing much apart from making an annoying rattling sound at low speeds. I quickly put them back in after a few short rides, because the front forks bottomed out in their absence. Same bike, same rider, same roads, same riding style . . . . they are back in and staying in.

YMMV etc
I guess I'll hang on to the pair I found in the fork I'm rebuilding. I'll leave them out for now tho. Maybe you need new springs, heavy duty?

Charlie
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Old 11-26-2011, 05:03 PM   #13
Max Headroom
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Originally Posted by disston View Post
I guess I'll hang on to the pair I found in the fork I'm rebuilding. I'll leave them out for now tho. Maybe you need new springs, heavy duty?

Charlie
Yeah, but I'm already running heavy duty springs out of an RS. I checked their length when I did the fork seals just to make sure they were OK. Static sag is where it should be, and the front end certainly doesn't feel soft. I've also fitted a cable tie around one of the stauchiions to see exactly how far the sliders move under braking which tends to confirm they are about right too.
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Old 11-27-2011, 08:56 AM   #14
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Quote:
Originally Posted by Max Headroom View Post
Yeah, but I'm already running heavy duty springs out of an RS. I checked their length when I did the fork seals just to make sure they were OK. Static sag is where it should be, and the front end certainly doesn't feel soft. I've also fitted a cable tie around one of the stauchiions to see exactly how far the sliders move under braking which tends to confirm they are about right too.
So one of the things you suspect is the noise you think is bottoming out is actually something else? Or is it the lack of movement that makes you think the forks have bottomed out? Misaligned tubes, sometimes called sticktion, can make the front end stop movement mid-way through passage. (sometimes I can't help being too wordy, Sorry 'bout that)

This is the main thing I'm trying to fix on my bike right now. I have 3 sets of forks and I'm trying to find the pair that is the straightest. After I get them going up and down well with no sticktion then I'll rebuild the dampers, get some new springs and install dual ATEs.

Charlie
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Old 11-27-2011, 09:33 AM   #15
Rob Farmer
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Originally Posted by bay View Post
.so now i can keep the ate brakes and concentrate on makeing the forks work a little better.does anyone know of a good solution.
Bay,

I had loads of problems with the ATE forks on an RS I rebuilt, I lost count of the number of times the forks came apart. It turned out the small piston rings on my dampers were worn and were letting oil past instead of through the damper mechanism. I also made the mistake of using Aeroshell oil from Motobins, this caused stichion problems with the forks. I fitted Belray 5 fork oil and new rings and it all worked a treat.

Once the forks were sorted I preferred the whole ATE setup (brakes with bar master cylinder and forks) to the Brembo front end setup on my 78 100/7.

I've tried both the RS springs and the standard springs in my bikes and much prefer the supple standard springs over the RS ones. If you go too high with the fork oil grade the forks quickly become too harsh.

There are 3 of the little dampers per fork leg


Rob Farmer screwed with this post 11-27-2011 at 09:41 AM
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