Converting from original Master Brake Cyl (under tank) to one on handlebar

Does anyone have any specific information on Converting from original Master Brake Cyl. (under tank) to one on handlebars? I only have a single disk system and do not need to go to 2 disks.


I understand it can be done, but I would like an itemized listing of all parts necessary, including part numbers, to go from under tank master cylinder to a 12 MM one on the handlebars. I understand that this procedure involves replacing the throttle cable assy. and going to another 1-into-2 throttle cable, adding a couple of hoses (one from handlebar down to backbone of frame, and one from backbone of frame down to front left fork tube.

I probably have all of the parts in stock except for the brake line (which we do custom on each bike). However, every time I've quoted someone here on the MOA forum the retail price of the new parts they back out. It's probably a $400~500 proposition. Control assembly, throttle, matching grip for other side, switch, cam.

If you're interested in new parts for this, PM me.

Boxerworks thread.

I am not recommending this solution and I haven't done the conversion, but I find this interesting.

http://forum.boxerworks.com/viewtopic.php?f=1&t=5461&hilit=handlebar+master+cylinder

There may be very good reasons not to do this conversion, but I bought a spare throttle assembly several years ago just in case
I ever want to do this.

I did the conversion on my 1977 R100RS, worked great but not cheap!

not cheap

but if you were able to stop 10 feet sooner and avoided a collision by 9 feet, wouldn't it be worth it?

dpmonk said:

but if you were able to stop 10 feet sooner and avoided a collision by 9 feet, wouldn't it be worth it?

Click to expand...

ThIs is the primary reason I converted my single disc brake to a front twin disc brake on my 1976 R75/6
Was it worth it's? Every nickel!

Single to dual disc conversion

b25bsaboy said:

ThIs is the primary reason I converted my single disc brake to a front twin disc brake on my 1976 R75/6
Was it worth it's? Every nickel!

Click to expand...

I'm about to do the same conversion, any pointers??

Single disc to twin disc

I'm in the process of converting from single to twin disc.


I took a left leg with the disc setup, sawed the tab off and had a buddy weld it on the other side. That leg will now be my right leg with the second disc. On my Classic Bavarian Bagger site I have the front wheel cleaned up and the second disc added for displayed. The pictue is on post 25 and 26. Just one way to do the conversion. This is being down on a '74 R90/6.

Very nice Barry. Usin the old noggin. Mcivering. Best hobby ever. Hat tip plus.

I converted my 1976 R75/6 to double ATE's plus handlebar master cylinder. A Brembo upgrade would have been better yet, but it finally stops adequately instead of inadequately. I used parts from a basket-case 1977 RS and got rid of the Lesters and the same time.

Before...



After...

jimmylee said:

Does anyone have any specific information on Converting from original Master Brake Cyl. (under tank) to one on handlebars? I only have a single disk system and do not need to go to 2 disks.


I understand it can be done, but I would like an itemized listing of all parts necessary, including part numbers, to go from under tank master cylinder to a 12 MM one on the handlebars. I understand that this procedure involves replacing the throttle cable assy. and going to another 1-into-2 throttle cable, adding a couple of hoses (one from handlebar down to backbone of frame, and one from backbone of frame down to front left fork tube.

Click to expand...

When BMW first did this, they used existing parts for the most part, by using a "Y" that mounted same place as the old undertank master cylinder was located. (not G/S, ST, R65) This meant same downstream metal lines and rubber lines could be used on RS and RT and the same rubber lines for CS and T models.

Later ... with the '85 models, they ceased using the Y and the hose from the master cylinder just went to the top of the fender. Of course the fender is different on those models, while up to 1984 it was the same as forever.

IMHO you can't do better than the one-into-two throttle cable setup, but it's not clear to me it's available for all carburetors from older models. There are without question, however, handlebar mount systems with dual cables. i.e. R100GS, etc. Back in the day when I replaced my '78 S with an '84 RS, I was really pleased with the one-into-two throttle cable system, as it simply eliminated the need for periodic carb synching due to cable stretch. I know there are different part numbers for the lower cables depending on whether 38 mm or 40 mm carbs, but don't know the physical differences as have simply never looked.

Any "itemized listing" needs to be custom designed for your specific bike.

... the more I think about it ...

For a single disc /7 or /6 it might be that the best solution may be R80G/S (maybe R80ST, too) parts. This bike also came with a single front disc, and the hose from the master cylinder simply drops straight down to the rubber-to-metal tube junction on the fork. A stock hose may be too long but in any event the parts pages will show a little clamp that mounts to the lower triple clamp to help keep the hose under control. Later (a little) R100GS parts may be similar and feature dual cables for the throttle if that's what you want.

lkchris said:

When BMW first did this, they used existing parts for the most part, by using a "Y" that mounted same place as the old undertank master cylinder was located. (not G/S, ST, R65) This meant same downstream metal lines and rubber lines could be used on RS and RT and the same rubber lines for CS and T models.

Later ... with the '85 models, they ceased using the Y and the hose from the master cylinder just went to the top of the fender. Of course the fender is different on those models, while up to 1984 it was the same as forever.

IMHO you can't do better than the one-into-two throttle cable setup, but it's not clear to me it's available for all carburetors from older models. There are without question, however, handlebar mount systems with dual cables. i.e. R100GS, etc. Back in the day when I replaced my '78 S with an '84 RS, I was really pleased with the one-into-two throttle cable system, as it simply eliminated the need for periodic carb synching due to cable stretch. I know there are different part numbers for the lower cables depending on whether 38 mm or 40 mm carbs, but don't know the physical differences as have simply never looked.

Any "itemized listing" needs to be custom designed for your specific bike.

... the more I think about it ...

For a single disc /7 or /6 it might be that the best solution may be R80G/S (maybe R80ST, too) parts. This bike also came with a single front disc, and the hose from the master cylinder simply drops straight down to the rubber-to-metal tube junction on the fork. A stock hose may be too long but in any event the parts pages will show a little clamp that mounts to the lower triple clamp to help keep the hose under control. Later (a little) R100GS parts may be similar and feature dual cables for the throttle if that's what you want.

Click to expand...

Just an FYI, concerning this.

I decided to go ahead and do the switch to the handlebar master cyl. I talked to Rusty at Max's BMW, and he was very helpful, and also understanding about my desire to not spend as much as possible.

I purchased (and received, but not installed yet) the M/C which includes the brake handle and all of those parts. I also had to purchase a new "gear" that pulls the throttle cables. I opted for the two-cable M/C hook-up so I would not have to purchase more throttle cables (i.e. the one-into-two arrangement). I also had to purchase the twist grip tube which also included the grip.

There was optional, the purchase of a "manifold" or "distributor" that mounts down where the old M/C used to reside on the back-bone of the frame. This is needed only if you don't purchase the brake light switch that also mounts on the handlebar, and needs to be re-wired by installer.

The manifold is necessary if you want to run your old brake light switch off the brake fluid pressure (as it did on the old set-up). So, the manifold is required for that. The only other "parts" needed are the two hoses (if opting to use the manifold setup), 1 from the handlebar to the manifold, and another to run from manifold down to upper end of fork tube connection. These cannot be sold by Max's unless they know exactly how long each must be (depends upon handlebar height, etc.) and even if they can provide them, Rusty told me that they get them made by a company in Dayton, OH, as these are not factory.

I found a local company (here in Greenville, SC) that has done many of these for other BMW's and other bikes, so I will take my components, including my home-made manifold (I am a programmer/machinist) to get them to make me custom hoses to match my length needs.

When I have completed job, I will include a write-up listing all my components, and their BMW part numbers, and also an engineering sketch of the manifold that I will design.

BMW, according to Rusty, did also offer a "manifold" on some models, so this part could have been purchased.

Thanks for your input.