Boxerworks.com

The time has come to convert my '76 R75/6 single disk brake, with under-the-tank master cylinder, to a dual disk setup with a handlebar mounted master cylinder. I already have that ever so necessary R/H fork slider and attendant caliper. Even so this will be a spendy proposition.

The first place I went was to Moto Bins in the UK.

http://www.motobins.co.uk/displayfinal. ... =&bike=991

They list two conversion kits, one for the '77 and up RS/RT bikes and one for all the others, which translates to the single disk bikes during the /6 and /7 period. Included in the kit is are the other necessary associated parts such as the new type throttle cable gear. And apparently a different R/H mirror is required with the later setup. All that is good, but what they don't talk about is whether the two kits have the same or different master cylinder bores, and if so what are they.

What I'm after with this post is simply to read any thoughts you might have on the subject, or if you know of any information or parts resources I might be overlooking. In particular I'd like to hear what handlebar mounted master cylinder bore you might recommend.

Also, should I source the necessary parts from somebody other than Moto Bins?

I'm leaning toward buying the single disk kit for my dual disk setup. I seem to remember somebody on the forum here saying that he's using the 13mm bore handlebar master cylinder with two swinging ATE calipers and he likes the way it feels. I also seem to remember Brad Belk being a bit disappointed with the conversion he made on his single disk R90/6. So I'm thinking that the smaller bore master cylinder would work pretty good with dual disks anyhow.



Ken

I got the handlebar m/c from Motobins for my '77RS. I think it came with a 15mm bore. Were I to do it again, I would try something a little smaller. I don't really have any complaints, but would feel more secure with a little more power. I've never really tried to squash it to see how fast it stops, its just a feeling.

"how fast it stops" ... I made an oxymoron.

Native /5 wrote:I got the handlebar m/c from Motobins for my '77RS. I think it came with a 15mm bore. Were I to do it again, I would try something a little smaller. I don't really have any complaints, but would feel more secure with a little more power. I've never really tried to squash it to see how fast it stops, its just a feeling.

"how fast it stops" ... I made an oxymoron.

I'm glad to hear that you might have preferred a smaller bore, glad for me anyhow. I still don't know if the master cylinder in the RS/RT kit has the same bore as that for the single disk bikes. But if there is a difference I would want at least the same bore, or preferably smaller. And from what you wrote you believe smaller would have been better for your RS.

By the way, I didn't know you have an RS--and the first year RS to boot! Was I just not paying much attention or, unlike me, were you just being modest about your penchant for buying airheads?

12 works good for single disc, 13 seems to be the one for duals.
although some like the 14.
15 is just too much.
Why are you buying from Motobins?
They don't seem that much cheaper, especially when you consider the shipping.
I would start with Chris over at Eurotechmotorsports.com
HE knows what you need.

Before he retired my local guy did 11 mm cylinders, and one works very well for me, but those that have never tried one dont seem to like them.

The bore for my single-disc is 13mm, FWIW.

wirewrkr wrote: Why are you buying from Motobins?
They don't seem that much cheaper, especially when you consider the shipping.
I would start with Chris over at Eurotechmotorsports.com
HE knows what you need.

The only reason I was/am considering Motobins is that I knew they made kits. Your advice is the sort of thing I'm looking for. One of the things I'll be doing right away (guess it will have to be Monday) will be to hook up with Chris at Eurotechmotorsports.

I'm looking forward to converting the R75/6 to a handlebar mounted master cylinder. I converted my '77 R100/7 with dual disks and the dual disk under the tank master cylinder. It was a decided improvement, but I'm sure a handlebar mounted master cylinder would have been significantly better.

If I had to make the decision right now, without gathering more information I would probably go with the 14 mm master cylinder bore. But that's based on too little input.


Ken

justoneoftheguys wrote:The bore for my single-disc is 13mm, FWIW.

I'm afraid that you experience won't be close enough to my situation to be meaningful Rob. You're talking about your R65 and it will have the hard mounted ATE caliper I believe; that or a Brembo. The twin swinging ATE calipers with which my R75/6 will be equipped makes it other than an apples to apples comparison. Aside from the caliper pistons being different in diameter, I believe your ATE caliper uses two pistons and my swinging ATE calipers use only one piston per caliper.



Ken

Ken in Oklahoma wrote:

justoneoftheguys wrote:The bore for my single-disc is 13mm, FWIW.

I'm afraid that you experience won't be close enough to my situation to be meaningful Rob. You're talking about your R65 and it will have the hard mounted ATE caliper I believe; that or a Brembo. The twin swinging ATE calipers with which my R75/6 will be equipped makes it other than an apples to apples comparison. Aside from the caliper pistons being different in diameter, I believe your ATE caliper uses two pistons and my swinging ATE calipers use only one piston per caliper.



Ken

I knew I put that "FWIW" in there for a reason!

IF ... my m/c is 15mm (too dark to check now), I would go with the 14mm in a do-over myself, Ken.

Yep, 1st year RS, converted to an S. Here's what "Sasquatch" looked like when I dragged it home. 'Cept it didn't have no handlebars nor wheels, that's why I dragged it...ain't she purty?