1973 850 Commando front brake M/C question

Jonez69

Jonez69

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I decided to replace my old front brake line while I was investigating other front end issues (see fork slider cracking thread posted earlier). Replaced the line with new braided stainless but the brake fluid was dirty so time to flush and clean everything and rebuild the caliper. I will need to order parts for that job, but the question I have concerns my master cylinder. It has the 13mm conversion kit installed and the smaller hole is blocked by the sleeve. Is this correct? The brakes miraculously worked before tear down, but shouldn't this orifice be open to the plunger? The sleeve has a hole for it. I'm very tempted to just buy the AN 13mm M/C complete and move on but thought I would ask about my old one first. Pardon my ignorance, I'm here to learn! Thanks!
1973 850 Commando front brake M/C question
1973 850 Commando front brake M/C question
 
Jonez69 said:
I decided to replace my old front brake line while I was investigating other front end issues (see fork slider cracking thread posted earlier). Replaced the line with new braided stainless but the brake fluid was dirty so time to flush and clean everything and rebuild the caliper. I will need to order parts for that job, but the question I have concerns my master cylinder. It has the 13mm conversion kit installed and the smaller hole is blocked by the sleeve. Is this correct? The brakes miraculously worked before tear down, but shouldn't this orifice be open to the plunger? The sleeve has a hole for it. I'm very tempted to just buy the AN 13mm M/C complete and move on but thought I would ask about my old one first. Pardon my ignorance, I'm here to learn! Thanks!View attachment 116655View attachment 116656
Click to expand...
I bought the re-sleeve kit from Don Pender (@madass140) and seem to recall instructions were to only drill one of the two holes out with the included small drill....then de-burr with a bit of fine emery on a rod. Has worked great for 7 or 8 yrs now.
 
My master cylinder has a number engraved on the back. I've seen this on M/Cs already rebuilt for sale on internet searches. So I believe this kit to be one installed and sold as a rebuilt M/C.
1973 850 Commando front brake M/C question
1973 850 Commando front brake M/C question
 
Jonez69 said:
I decided to replace my old front brake line while I was investigating other front end issues (see fork slider cracking thread posted earlier). Replaced the line with new braided stainless but the brake fluid was dirty so time to flush and clean everything and rebuild the caliper. I will need to order parts for that job, but the question I have concerns my master cylinder. It has the 13mm conversion kit installed and the smaller hole is blocked by the sleeve. Is this correct? The brakes miraculously worked before tear down, but shouldn't this orifice be open to the plunger? The sleeve has a hole for it. I'm very tempted to just buy the AN 13mm M/C complete and move on but thought I would ask about my old one first. Pardon my ignorance, I'm here to learn! Thanks!View attachment 116655View attachment 116656
Click to expand...
" It has the 13mm conversion kit installed and the smaller hole is blocked by the sleeve. Is this correct?"


Yes.
That is how it's designed.
It's a bitch to bleed.
Bench bleed first
 
Last edited:
I thought about getting a sleeve kit for my mk3 but in the end I went with the new A/N 13mm master cylinder, bolt on - no worries about a sleeve moving inside the original master cylinder.
It may cost more but at the end of the day you have a brand-new master cylinder.
 
I'm a fan of the RGM sleeve kit. The bronze sleeve is screwed into the M/C and you can adjust the lever to piston distance to 'tune' the M/c relief to reservoir point. Something that you cannot do with the new M/c unless you can make top hatted shims to sit on the piston itself.
 
Thanks to all for the replies! Nice to know that my current M/C is functional but I have decided to purchase a new AN 13 mm. My riding season is fast approaching its end, but maybe with a bit of luck I will have the parts here in a couple of weeks and perhaps a long test ride before winterizing the bike.
Thanks again!
 
Call me a contrarian - go ahead, I am :)

I would never sleeve a standard Norton M/C. I would never knowingly ride a Norton with a sleeved M/C. I would never replace a working standard Norton M/C just to have a 13mm version. If I needed a new Norton M/C I would buy the 13mm version.

Why? Too many stories of sleeve problems and stopping only has to do with the pressure placed on the P.O.S. caliper pistons and therefore pads. The standard and 13mm M/C can both produce the same pressure but the 13mm requires less grip strength - that's their value. Of course, if you don't have the grip strength, then that would be a reason to change.

Yes, I have ridden Nortons with both and they all stop just as poorly :)
 
grandpaul said:
Strange, I think they stop just fine.

Then again, I'm not a top-level rider and always make it a point to ride withing my, and the bike's, limitations...
Click to expand...
I could say the same about my 66 Triumph 500 which would only stop a little better than Fred Flintstones feet.

When you switch back and forth between a 74 850 Commando and a 74 Trident, both with stock brakes, you certainly know that Lockheed was able to make better brakes than what they made for Norton.

And, you have/have had much more sophisticated bikes so I'm sure you know that vintage Nortons are not great at stopping no matter the M/C.

Now you're being the contrarian :)
 
marshg246 said:
I could say the same about my 66 Triumph 500 which would only stop a little better than Fred Flintstones feet.

When you switch back and forth between a 74 850 Commando and a 74 Trident, both with stock brakes, you certainly know that Lockheed was able to make better brakes than what they made for Norton.

And, you have/have had much more sophisticated bikes so I'm sure you know that vintage Nortons are not great at stopping no matter the M/C.

Now you're being the contrarian
Click to expand...
My only answer is that I really am not a "top rider", and don't find a significant difference between the Triumph and Norton disc brakes. Of course it's been a good few years since I sold my last Trident, so my memory won't help me to parse the finer nuances...
 
Jonez69 said:
I decided to replace my old front brake line while I was investigating other front end issues (see fork slider cracking thread posted earlier). Replaced the line with new braided stainless but the brake fluid was dirty so time to flush and clean everything and rebuild the caliper. I will need to order parts for that job, but the question I have concerns my master cylinder. It has the 13mm conversion kit installed and the smaller hole is blocked by the sleeve. Is this correct? The brakes miraculously worked before tear down, but shouldn't this orifice be open to the plunger? The sleeve has a hole for it. I'm very tempted to just buy the AN 13mm M/C complete and move on but thought I would ask about my old one first. Pardon my ignorance, I'm here to learn! Thanks!
Click to expand...

Regarding the original post, do you know the source of the 13mm conversion kit?
The sleeve that comes with the RGM kit has grooves around its circumference where the holes are that allow flow even if the hole in the sleeve is not aligned with the hole in the original MC.
1973 850 Commando front brake M/C question
 
Jonez69 said:
My master cylinder has a number engraved on the back. I've seen this on M/Cs already rebuilt for sale on internet searches. So I believe this kit to be one installed and sold as a rebuilt M/C.
Click to expand...
I have a MC that has not been sleeved that has a similar marking.
 
marshg246 said:
Call me a contrarian - go ahead, I am :)

I would never sleeve a standard Norton M/C. I would never knowingly ride a Norton with a sleeved M/C. I would never replace a working standard Norton M/C just to have a 13mm version. If I needed a new Norton M/C I would buy the 13mm version.

Why? Too many stories of sleeve problems and stopping only has to do with the pressure placed on the P.O.S. caliper pistons and therefore pads. The standard and 13mm M/C can both produce the same pressure but the 13mm requires less grip strength - that's their value. Of course, if you don't have the grip strength, then that would be a reason to change.

Yes, I have ridden Nortons with both and they all stop just as poorly :)
Click to expand...
Are all MC conversion kits created equal? They are talked about here generically, but is there any information about which specific kits were involved when failures occurred?
With the RGM kit, the MC is tapped for the threaded sleeve. It seems to me that it shouldn't be able to slip.
 
The two sleeved MCs that failed on my Commando were both from a company that was recommended on various Norton Forums. Their comment after the second failure was, "Wow, two failed? That shouldn't happen!" Really, ya think?
 
NickZ said:
Are all MC conversion kits created equal? They are talked about here generically, but is there any information about which specific kits were involved when failures occurred?
With the RGM kit, the MC is tapped for the threaded sleeve. It seems to me that it shouldn't be able to slip.
Click to expand...
I have no idea. I'm not trying to bash RGM and I do use/sell some of their products, but they often have quality control issues from batch to batch. I don't know if that applies to their conversion or not. As always, when people relate stories about such things failing, it would be nice if they stated who made the failed part.

BTW, reading the RGM instructions, they repeatedly state not to do it if you don't have the skills and/or equipment. They say a drill press will do and an angle block to hold the M/C. Get the tapping right and you're good, screw-up and throw it away. What does it cost when you send them the M/C for upgrade? They already say they do them in batches approx. every 10 weeks. Also, I cannot find the kit for sale on their site - just some of the replacement parts.
 
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