Sleeved master cylinder

Hi All,
Yesterday I installed a reduced master cylinder kit on my 74 850 roadster.
The instructions were very good but full of dire warnings about the dangers of inept and unskilled attempts to do the conversion.
With this in mind I proceeded with patience and care.
The job went smoothly , exactly to instructions but on the way I made an interesting discovery
On returning the bike to the road some weeks ago I couldn’t believe how bad the front brake was. Yes, I remembered it as being wooden and requiring an iron grip but now I found it useless, had the ravages of time debilitated me to the point where I couldn’t use a brake lever?
On disassembly I found the bleed holes into the reservoir absolutely blocked solid! No, not a bit gummed up requiring a bit of wire to clean them but full of cement, obviously degraded brake fluid and moisture. At first I didn’t recognise that there was two orifices. I thought I was just looking at a casting fault. It required drilling out using an appropriate size drill bit , The piston was rusted externally and I had great difficulty in removing it. It’s amazing that the seals were still working.
With the new sleeve installed I played with the lever adjustment screw that was part of the kit to try and get a degree of useablity.
So, how are the brakes now? Much much better, not brilliant, exactly as advertised by the manufacturer of the kit.
The problem being the appalling geometry and shape of the standard lever. Although I have a large hand, I battle to get my little finger around the brake lever as it sweeps away from the hand grip, Dupytrens contracture not helping. The brakes are definitely still not a two finger operation. The slight sponginess doesn’t worry me. I took the bike for a very pleasant test ride on nearby quiet country roads letting it gently accelerate up to about 5500 rpm which must be approaching 90mph and giving it some solid stops.
I am now mucking about shimming the contact pad of the brake lever trying to bring it closer to the grips to make it easier to grab in an emergency.
Short of fitting a second disc are there any other improvements I can make to the brakes? As the bike is very original I don’t want to make obvious external changes.
I have heard that the Ferodo Platinum brake pads give the best results. Does anyone know if it is true?
regards
al

There are several 13 mm sleeve kits out there, Al Miles, RGM, and Don Pender (Madass 140) to name three. Which unit do you have? I have personal experience with the Al Miles and RGM kits. These are all different approaches to the same end result. Al Miles sells his conversion on an exchange basis, but RGM will sell the kit for DIY or perform the labor. I believe Don Pender offers the same option. If you installed the kit yourself, then obviously clearing the bleed holes after boring for the sleeve should be done before the installation of the sleeve. It is possible that the holes became blocked with swarf from the boring process. The kits should also have been supplied with a new piston. If the piston rusted, this would indicate moisture in the system.

I have a Miles cylinder on one bike with the stock disc and caliper with Ferodo Platinum pads. It is an improvement, but I have two other bikes with 13 mm sleeved cylinders, one RGM and one Miles, both with 4 piston Brembo caliper and 300 mm floating discs. These are an order of magnitude better. One advantage of the RGM kit is there is an adjustable piston 'pusher' which can be used to adjust piston return and/or lever travel.

I hope this helps.

Miles kit doesn't use the second bleed hole. Madass is different, more like the original. I have pics of both but didn't want to post them in fear of pissing someone off. Bought a Andover Norton Master cylinder, no difference. I went thru this months ago! PIA I have bled the break from top, master cylinder , to bottom caliper. Bottom to top. And still have spongy front breaks. The best forum explanation was there is an area in the caliper that will not bleed all the air out. I have decided to ride the bike and hope the bubble gets moved . Good luck.

mean gene said:

Miles kit doesn't use the second bleed hole. Madass is different, more like the original. I have pics of both but didn't want to post them in fear of pissing someone off. Bought a Andover Norton Master cylinder, no difference. I went thru this months ago! PIA I have bled the break from top, master cylinder , to bottom caliper. Bottom to top. And still have spongy front breaks. The best forum explanation was there is an area in the caliper that will not bleed all the air out. I have decided to ride the bike and hope the bubble gets moved . Good luck.

Click to expand...

This from Old Britts is the only way I got all the air out:


BLEEDING THE NEW BRAKE ASSEMBLY
NOTE: PUMPING� WILL NOT BLEED YOUR NEW BRAKE SYSTEM.

Before attaching the master cylinder to the handlebar, bleed the brake system. Start by draping a few rags across the valley between the handlebars and the headlight. Attach the reservoir cap and gasket to the reservoir. Slip a �� box wrench over the bleed valve of the caliper. Attach the short length of vinyl tube (found inside the syringe housing) to the end of the syringe (provided). Draw fresh brake fluid into the syringe unit the syringe is full. Using the syringe, deposit a little brake fluid at the opening of the bleed valve. Depositing the little brake fluid at the bleed valve opening causes a meniscus to form over the bleed valve opening. This meniscus or bubble of brake fluid displaces any air at the opening of the bleed valve. Displacing air at the opening prevents any air bubbles from being injected when the bleed valve is opened. This is especially important if additional bleeding is required. Force the open end of the vinyl tube over the bleed valve. Make sure there are no air bubbles present at the open end of the vinyl tube. If air bubbles are present, remove the syringe with the vinyl tube attached, squirt a little fluid out of the syringe and then reattach the syringe and tube. Open the bleed valve slightly. While holding the master cylinder vertically in one hand, slowly begin to inject brake fluid into the caliper with the other hand. As you inject the fluid, rotate the upper end of the master cylinder in a circle. Holding the master cylinder vertically and rotating the upper end in a circle which injecting the brake fluid into the caliper insures that all air bubble will be forced out of the line and into the reservoir. Do not fully depress the plunger of the syringe. Stopping the plunger early will prevent injecting the always-present air at the end of the plunger. Leaving a little fluid in the syringe insures against injecting air bubbles into the caliper housing. When almost all the fluid is gone from the syringe, close the bleed valve, set the master cylinder on the rages placed across the handlebars and remove the syringe with the vinyl tube still attached. Reload the syringe and repeat the above operation to insure all bubbles have been displaced. The syringe holds 12 cubic centimeters of fluid. The reservoir will comfortably hold 24 cubic centimeters. If it becomes necessary to bleed beyond two full syringes, some of the fluid may need to be removed from the reservoir.

When I fitted Don's resleeve kit, had a heck of a job getting any braking force at the pads. Turned out I had not got the lever contact point correct so the piston seals were not correctly positioned within the bore length relative to the two reservoir holes. Needs to be just before the holes when at rest to minimize wasted lever travel.
Also had typical bleed issues other report. After doing all suggestions, reverse bleeding, leaving over night with lever tied in to bar etc, what ultimately worked was rapidly flicking lever 50+ time while observing the open reservoir. I suddenly saw a couple of tiny, tiny micro bubbles float up out the holes. Everything went firm and has stayed that way three seasons.

Fedoro Platinums seem to work quite well on stock rotor. These were first pads i've had on this bike so cannot report how other types perform. I'd say braking is nearly as good as my modern Bonneville front disc.

Alan L said:

Hi All,
Yesterday I installed a reduced master cylinder kit on my 74 850 roadster.
The instructions were very good but full of dire warnings about the dangers of inept and unskilled attempts to do the conversion.
With this in mind I proceeded with patience and care.
The job went smoothly , exactly to instructions but on the way I made an interesting discovery
On returning the bike to the road some weeks ago I couldn’t believe how bad the front brake was. Yes, I remembered it as being wooden and requiring an iron grip but now I found it useless, had the ravages of time debilitated me to the point where I couldn’t use a brake lever?
On disassembly I found the bleed holes into the reservoir absolutely blocked solid! No, not a bit gummed up requiring a bit of wire to clean them but full of cement, obviously degraded brake fluid and moisture. At first I didn’t recognise that there was two orifices. I thought I was just looking at a casting fault. It required drilling out using an appropriate size drill bit , The piston was rusted externally and I had great difficulty in removing it. It’s amazing that the seals were still working.
With the new sleeve installed I played with the lever adjustment screw that was part of the kit to try and get a degree of useablity.
So, how are the brakes now? Much much better, not brilliant, exactly as advertised by the manufacturer of the kit.
The problem being the appalling geometry and shape of the standard lever. Although I have a large hand, I battle to get my little finger around the brake lever as it sweeps away from the hand grip, Dupytrens contracture not helping. The brakes are definitely still not a two finger operation. The slight sponginess doesn’t worry me. I took the bike for a very pleasant test ride on nearby quiet country roads letting it gently accelerate up to about 5500 rpm which must be approaching 90mph and giving it some solid stops.
I am now mucking about shimming the contact pad of the brake lever trying to bring it closer to the grips to make it easier to grab in an emergency.
Short of fitting a second disc are there any other improvements I can make to the brakes? As the bike is very original I don’t want to make obvious external changes.
I have heard that the Ferodo Platinum brake pads give the best results. Does anyone know if it is true?
regards
al

Click to expand...

Al, did you also strip the caliper? If not chances are that the fluid ways are blocked by the same type of crud you found in the m/cyl. It sounds as though the fluid has not been replaced regularly and has absorbed moisture leading to the rust you saw, so the caliper pistons may also be in the same state.

Hoses?

Hi

Ron L said:

There are several 13 mm sleeve kits out there, Al Miles, RGM, and Don Pender (Madass 140) to name three. Which unit do you have? I have personal experience with the Al Miles and RGM kits. These are all different approaches to the same end result. Al Miles sells his conversion on an exchange basis, but RGM will sell the kit for DIY or perform the labor. I believe Don Pender offers the same option. If you installed the kit yourself, then obviously clearing the bleed holes after boring for the sleeve should be done before the installation of the sleeve. It is possible that the holes became blocked with swarf from the boring process. The kits should also have been supplied with a new piston. If the piston rusted, this would indicate moisture in the system.

I have a Miles cylinder on one bike with the stock disc and caliper with Ferodo Platinum pads. It is an improvement, but I have two other bikes with 13 mm sleeved cylinders, one RGM and one Miles, both with 4 piston Brembo caliper and 300 mm floating discs. These are an order of magnitude better. One advantage of the RGM kit is there is an adjustable piston 'pusher' which can be used to adjust piston return and/or lever travel.

I hope this helps.

Click to expand...

Hi Ron,
It is an RGM kit. I don’t know how it compares to the other kits but I have no complaints whatsoever. It has clear instructions and does what it says it does. I had to purchase a 16mm reduced shank drill bit and an 18.5x1.5 tap but that’s ok.
Even with existing brake hoses the brake isn’t excessively spongy. I have no intention to go to braided stainless hoses at this stage.
I think you misunderstood what I said about the blocked holes from the reservoir to the master cylinder and the rust. That was the condition I found the master cylinder in before I converted it to the smaller bore size. Everything is now cleaned up and pristine.
Again, I am happy with the results but the actual design of the original master cylinder leaves a lot to be desired. How someone with a small hand could quickly grab a handful of brake in an emergency is beyond me. As I said previously, I have been adjusting the lever so it doesn’t sit so far from the grips.
One thing I do disagree with is the assertion in the RGM instructions (and elsewhere) that 50 years ago brakes didn’t have to be as effective as other vehicles sharing the road also didn’t have great brakes. I can assure the reader that when a kangaroo jumps out in front of you (and there are thousands of them around here), that an emergency stop was just as important in 1970 as it is now.
Again, any suggestions or recommendations on how to further improve my brakes would be greatly appreciated.
regards al

Hi c

cliffa said:

Al, did you also strip the caliper? If not chances are that the fluid ways are blocked by the same type of crud you found in the m/cyl. It sounds as though the fluid has not been replaced regularly and has absorbed moisture leading to the rust you saw, so the caliper pistons may also be in the same state.

Click to expand...

hi cliff,
stripping and cleaning the calliper will be my next job.

Going to 13mm and stripping the chrome off the disc was an improvement for sure but ultimately the brake was never as good as I wanted until I put a 12" disc and AP clone caliper. It's never going to be like my dual disc rice bikes were but I'm very happy with it.

As for the stock look: I had people tell me that "those old bikes never had disc brakes" even with the originals still on it. I'm happy to tell folks the brake is a concession to distracted drivers.

Best option IMHO is a nice new Brembo master cylinder. Already the right bore, and a nice adjustable reach dog leg lever. Sorted.

Alan L said:

Even with existing brake hoses the brake isn’t excessively spongy. I have no intention to go to braided stainless hoses at this stage.

Click to expand...

You will be surprised how much difference, they may not look as if they are bulging but the stainless braided will make a difference regardless.

The Madass140 kit is 1/2" not 13mm so a better ratio.

His price and bore of 1/2" are tough to beat.

Onder said:

His price and bore of 1/2" are tough to beat.

Click to expand...

The trade-off is a somewhat longer lever travel with the 1/2" (12.7 mm) bore.

I like longer travel.

I MADE MY OWN 12MM MODIFICATION. A BLOODY GOOD BRAKE NOW. [ Didn't like thew RGM kit so sent it back. Personal preference. I still buy from RGM though. Good people ]