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Any of you have experience with the Motobins kit (61170) and SINGLE disc setup? Because I spoke with someone there just now, and it's not clear how I would go about installing this on a single disc. I would have to rework the flexible line that goes to the fork bracket or something?

Duane Ausherman wrote:The /5 drum brake was far better than the single disc. The official stopping distance required notice by the USA government even showed that it was not as good as the /5.

In the first week of our first /6 we knew that something was wrong. One can go to the double disc such as on the R90S, but then you have a super heavy fork that doesn't handle well.

Get the good stuff and forget it.

I've owned two R90S models, and one R90/6, and rode them collectively for 12 years or so, for tens of thousands of miles, and through some number of typical on-the-road "close scrapes" that I think most motorcyclists experience. The S bikes had dual ATE disc brakes; the R90/6 had a single ATE disc brake. All three motorcycles stopped adequately by my not-too-demanding standards. I've also owned a monoshock R80, and currently ride a 1984 R100RT, and both of these bikes have dual Brembo front brakes. They stop adequately, too. The Brembo-equipped bikes may require somewhat less grip to stop, but I certainly never felt like I needed to "drag my feet" to stop my /6 bikes. On the other hand, I never did any measurements to compare my bikes' braking performances, so I have no science to back up my claims---just lots of miles in the saddles of five different /6 and /7 motorcycles.

I think the primary "danger" of the under-tank master cylinder is not its ineffectiveness when well-maintained, but that its concealed location may lead to a lack of maintenance. Sheltered up underneath the tank, it's actually out of the weather and direct moisture that speeds up fluid degradation and internal hydraulic corrosion, but it's also easily forgotten and neglected. The handlebar-mounted master cylinders put the hydraulic system out in the open where it's difficult to ignore and forget about.

I googled "R90/6 road test" last night and read a review of the 1974 R90/6 from "Cycle Guide" magazine. There were no complaints about the then-new single disc brake, and certainly no claim that the drum brakes on the /5 bikes had been better than the single disc. The ATE disc brakes, both dual and single-disc, were standard equipment on airheads for 7 model years ('74 through '80)--- nearly twice as long as the cable-operated front drums on the /5s. Most tellingly, there wasn't any "front drum brake retrofit kit" marketed by San Jose BMW, Luftmeister, or by any other '70s/'80s after-market sellers of "go-fast" airhead equipment before the Brembo-equipped bikes came along in 1981. Brembo calipers and/or hydraulics may be an improvement worth buying from an ease-of-maintenance and use standpoint, but I'm certainly not convinced of any danger from ineffective front brakes on an adequately-maintained ATE-equipped bike.

Opinions obviously do vary.

khittner1 wrote: . . . Opinions obviously do vary.

Indeed they do, as does the quality of brake maintenance. My experience has the dual disks clearly coming out on top. I converted my '77 R100/7 from single disk to dual disk, using the larger bore under tank master cylinder. The difference, for me, was remarkable, and well worth the doing.

Ken

No regrets about that "super heavy fork", Ken?

khittner1 wrote:No regrets about that "super heavy fork", Ken?

Nah! One disk or two makes little difference in my lap times over the Talimena Scenic Drive. Confidence factor yes, lap times no.


Ken

I have a R90/6 with the handlebar conversion and a 1982 with Brembos, the Brembos are better brakes by a reasonable margin, but I would not be adverse to going to a Smaller MC on the 82.

If you have got big hands, then maybe the standard ATEs will work Ok for you. But the big difference with with a suitable sized MC you have progressive brakes that can be easily modulated, rather than the very wooden brakes of the original setup. traffic speeds and volumes have changed so much in the last 40 years, you need the best brakes even on our relatively slow bikes.

1970s road tests seemed to gloss over faults in many bikes, how often was the unreliability of Nortons commented on?

chasbmw wrote:. . . 1970s road tests seemed to gloss over faults in many bikes, how often was the unreliability of Nortons commented on?

Indeed! I've seen quite a few mags from the 50's doing a road test on a bike. They never said anything negative about them. But at least they let the potential buyer know that that "the controls fell readily to hand."

Anybody remember lusting for the Norton girl? (Hint: Google Norton Girl and look at the images.)

Ken

The copy in some of those Norton ads is as entertaining as the imagery. "Really, Hon---I was just reading the ad."

The motobins kit I bought several years ago was set up for a twin disc rig. Not to worry, the aluminum fluid divider is essentially the front half of the original under tank MC. 1 hose goes in, 2 hoses come out. Since you only have 1 disc, you need a bleeder screw to plug the un used outlet, (very simple). It may or may not be great, but it is SO much better than what you're used to, it will seem fantastic.

Lifebeat wrote: A question that you guys could maybe answer, it comes with an aluminium fluid divider (the kit # is : 61170), if I only have One disc and caliper, can I just not use it and bolt the hose directly to the caliper? I'm also assuming that the hose supplied connects to the original bracket on the left fork tube right?

OH! And BTW, any insight on the light switch issue?

Thanks a bunch!

I think you would be fine to put the top end of the brake line directly into the master cylinder. Either a direct male fitting or a banjo.