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Old 04-24-2010, 09:17 AM   #151
Renner
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Personally, I like the look of the twin ATEs, though it's generally understood the later Brembos are a step up in braking performance with less weight.

I'm rarely riding up to the edge of where that makes much of a difference.

+1 on the congrats Lornce.
I didn't notice when you passed the R50/5 along to the next person (not seeing it in you PP).

Renner screwed with this post 04-24-2010 at 09:24 AM
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Old 04-24-2010, 03:04 PM   #152
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Well, well, well.... Now you've done it. You're in the gang now!

I'm glad that you got the bike and really hope that you'll enjoy working on and riding it. Theres nothing quite like the R-90/6 series. Similar power to the R-100, less vibes, better mileage, great mid-range/roll-on performance and good looks.

You're far ahead of the game with dual disks installed already and wirewrkr is right. When the trans finally goes, replace it with one from a later bike. In fact, if you install a mid-8os trans along with the non-flywheel clutch assembly, you'll be doing yourself a huge favor. The work better, last longer and the engine will rev faster.

I'm so sorry and pissed that the mechanic ruined my R90s engine but I'm still looking forward to the Big Valve R-100!
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Old 04-24-2010, 04:50 PM   #153
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Congrats! Those twin discs are a nice upgrade. I'm still running the single un-drilled ATE on my '74. Thinking about the upgrade, especially pulling the hack.
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Old 04-24-2010, 07:30 PM   #154
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A single ATE caliper and solid rotor, ala '74 /6, were the Original anti-lock brakes. A /5 drum works better.

Back in '83 a '74 R90/6 was my first BMW. Went 20k miles that season up and down the eastern seaboard and New England states. Only rarely been without an airhead since. Just smooth, comfortable, practical and robust motorcycles.

Not sure where I'm going with this. Maybe find some /6 bodywork and return it to it's original stoic utility?

Anybody here want to trade a decent set of fenders and large /6 tank (preferably in original paint and pins, preferably black) and /6 Corbin seat for this R90S livery? I'd go straight up - S fairing, 90S tank, seat, cowl, side covers and fenders for the right stuff.



The mechanicals *appear* to be fairly sound. The PO (an extraordinarily decent fellow originally from NH now living in Toronto and moving to Manila next month) reported no issues with the trans and etc. He rode it 10 years before parking it 2-1/2 years ago to fix a toasted starter-motor.

Wouldn't mind a bar mounted 12mm master cylinder if I fell over one at the right price. It's already wearing braided lines from the stock master cylinder, so the existing brakes probably aren't too, too bad. Bar mount master cylinder would require a custom junction under the tank in order to use the existing stainless lines. Some cobbling required.

We shall see...

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Old 04-24-2010, 08:09 PM   #155
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Quote:
Originally Posted by Lornce
A single ATE caliper and solid rotor, ala '74 /6, were the Original anti-lock brakes. A /5 drum works better.

Back in '83 a '74 R90/6 was my first BMW. Went 20k miles that season up and down the eastern seaboard and New England states. Only rarely been without an airhead since. Just smooth, comfortable, practical and robust motorcycles.

Not sure where I'm going with this. Maybe find some /6 bodywork and return it to it's original stoic utility?

Anybody here want to trade a decent set of fenders and large /6 tank (preferably in original paint and pins, preferably black) and /6 Corbin seat for this R90S livery? I'd go straight up - S fairing, 90S tank, seat, cowl, side covers and fenders for the right stuff.



The mechanicals *appear* to be fairly sound. The PO (an extraordinarily decent fellow originally from NH now living in Toronto and moving to Manila next month) reported no issues with the trans and etc. He rode it 10 years before parking it 2-1/2 years ago to fix a toasted starter-motor.

Wouldn't mind a bar mounted 12mm master cylinder if I fell over one at the right price. It's already wearing braided lines from the stock master cylinder, so the existing brakes probably aren't too, too bad. Bar mount master cylinder would require a custom junction under the tank in order to use the existing stainless lines. Some cobbling required.

We shall see...

The junction under the tank is a stock item, used from 1981-1984 on the "big" bikes
the 12 mm is too small for the dual brakes, a 13mm is the one that works the best on the dual Ates.
Also, they never made a master assembly with dual cables and 12 mm.
The one you want would be from a single disc brembo setup, 85 and up mono lever.
you'll need to find a way to adapt the early switches onto the late controls. It's doable.
Robert
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Old 04-24-2010, 08:29 PM   #156
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Quote:
Originally Posted by wirewrkr
The junction under the tank is a stock item, used from 1981-1984 on the "big" bikes
the 12 mm is too small for the dual brakes, a 13mm is the one that works the best on the dual Ates.
Also, they never made a master assembly with dual cables and 12 mm.
The one you want would be from a single disc brembo setup, 85 and up mono lever.
you'll need to find a way to adapt the early switches onto the late controls. It's doable.
Robert
12mm is the master cylinder I'd prefer to use. It'd be the most powerful ATE brake you could cobble together using stock parts. Anything post '81 would be suitable. Single cable/dual cable - either could/would work just fine.

The post '81 junction wasn't made to suit a pair of '74 type braided lines. Hence the need for a custom junction to adapt a 12mm bar mounted m/c to the braided twin lines that are already on the bike.

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Old 04-25-2010, 02:30 AM   #157
Hawk Medicine
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Quote:
Originally Posted by Lornce
12mm is the master cylinder I'd prefer to use. It'd be the most powerful ATE brake you could cobble together using stock parts. Anything post '81 would be suitable. Single cable/dual cable - either could/would work just fine.

The post '81 junction wasn't made to suit a pair of '74 type braided lines. Hence the need for a custom junction to adapt a 12mm bar mounted m/c to the braided twin lines that are already on the bike.


You need this:








************



It's the way I set up My R90/6 anyway...!




+++++++++++++
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Old 04-25-2010, 02:59 AM   #158
carpetburn
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when i converted my 75/6 to dual ates, both solid discs[as i already had 1] i used a mono lever mastercylinder 13mm with a dual banjo[at the mastercylinder] and 2 braided lines, to bleed it was a major learning curve in that i ended up taking the mastercylinder off the handlebar and holding on an angle[throttle end pointing to the sky to get the bubbles out]. it was well worth the effort-being able to stop really is inspiring.
i purchased all parts on ebay as they turned up at the right price

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Old 04-25-2010, 05:37 AM   #159
Bill Harris
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Quote:
Originally Posted by Lornce
I only just figured out your user name reads "my mind's okay".

I always thought it was "my mind sock".
OMG, you're right. Epiphany time.

Quote:
Originally Posted by Anton
It's probably an OK value but why the hysteria?
Naysayer.

Congrats, Lornce.

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Old 04-25-2010, 07:18 AM   #160
wirewrkr
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Quote:
Originally Posted by Lornce
12mm is the master cylinder I'd prefer to use. It'd be the most powerful ATE brake you could cobble together using stock parts. Anything post '81 would be suitable. Single cable/dual cable - either could/would work just fine.

The post '81 junction wasn't made to suit a pair of '74 type braided lines. Hence the need for a custom junction to adapt a 12mm bar mounted m/c to the braided twin lines that are already on the bike.

Boy. all these years (16) I've been doing it this way and selling these parts to my customers, I've been wrong! Holy crap I better hunt all those guys down and tell them that their brakes don't really work.
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Old 04-25-2010, 08:35 AM   #161
AntonLargiader
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Quote:
Originally Posted by wirewrkr
One other negative about the 74 bikes, there's no clean way to do a handlebar mounted Master cylinder conversion due to the /5 style controls.
Since I like the /5 controls, I would probably go with some radial MC with a remote reservoir (for less visual bulk) provided the clamp would fit under the throttle cables.
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Old 04-25-2010, 09:19 AM   #162
Lornce OP
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Quote:
Originally Posted by wirewrkr
Boy. all these years (16) I've been doing it this way and selling these parts to my customers, I've been wrong! Holy crap I better hunt all those guys down and tell them that their brakes don't really work.
You mean the /6 spec braided lines I already have will fit a post '81 splitter junction?



I'd be happy to be wrong about that.

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Old 04-25-2010, 11:08 AM   #163
wirewrkr
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Quote:
Originally Posted by Lornce
You mean the /6 spec braided lines I already have will fit a post '81 splitter junction?



I'd be happy to be wrong about that.

Then be happy. Listen and learn.
The 13mm master cylinder is the one you need for your dual brakes.
Trust me.
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Old 04-25-2010, 11:16 AM   #164
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Originally Posted by wirewrkr
Then be happy. Listen and learn.
The 13mm master cylinder is the one you need for your dual brakes.
Trust me.

Okay, I'm sold on the splitter. Thanks for the heads up.

How come you figure I need a 13mm master cylinder?

I'd prefer the hydraulic advantage of the 12mm - even if it means a single throttle line and attendent throttle cable splitter.

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Old 04-25-2010, 12:12 PM   #165
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Quote:
Originally Posted by Lornce
Okay, I'm sold on the splitter. Thanks for the heads up.

How come you figure I need a 13mm master cylinder?

I'd prefer the hydraulic advantage of the 12mm - even if it means a single throttle line and attendent throttle cable splitter.

Volume. it's not all about the hydraulic theories. You have to have the volume of fluid as well. If it's too ascued one way or another, you get either too hard a feel with no hydraulic "leverage", (which is what happens with too much master cylinder bore), or not enough hardness at the lever as the fluid is trying to move to a bore that is too big.
(too small a master cylinder bore).
Some of us in the business have experimented for years on bikes until we came up with the basics for ATE conversion. 12mm is ideal for single, 13 is ideal for duals.
Other sizes work but aren't as efficient.
An example, I bought a used 1975 R90/6 about 5 years ago from a customer of mine who was bored with it. He had had the local dealer install a 14mm handlebar master and was never happy with the results.
It was actually worse that a properly adjusted /6 under tank unit.
I had a 13 in the shop and installed that and it was 20% better than the stock /6.
Still was too stiff, cramped the hand in a hard stop.
I bought a 12mm master cylinder and installed that on the perch and it worked much better. Along with a stainless steel line from our inmate bmwrench, I would say that there was a 35-40% improvement over stock under tank.
Over the years 3 different old school dealers have trusted me and paid me handsomely to know these things.
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