Brake m/c bore hone

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stanthomas

stanthomas

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Does anyone have experience of using a hone, such as Flex-Hone® , to clean up the bore on a Commando front brake master cylinder?

Any recommendations on abrasive type and grit?


Reason - corrosion from neglect has left some pitting in the cylinder bore and it seems to be leaking slightly. If it was external, a polish with 1000-grit wet 'n dry followed by Solvol would clean it up nicely.
 
If it doesn't clean up there are the 13mm sleeve kits that enhance breaking reasonable cost!
 
mean gene said:
If it doesn't clean up there are the 13mm sleeve kits that enhance breaking reasonable cost!
Click to expand...
Thanks, but I want to keep the bore at 5/8 so I am exploring options for renovating the original master cylinder.
 
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Explore the bore with a dental probe. If it hangs up in the pits, you are probably out of luck in terms of honing.
But you aren't risking much. Either it stops leaking or it doesn't.
To elaborate on mean gene's comments, if it won't clean up it would be a good excuse to sleeve it undersize to 13mm. You would still be using the original master cylinder.
Or, if you want to be really faithful to originality, you can bore and sleeve it back to stock bore size. Not the best idea, IMHO. But very doable. And you can use a readily available stock rebuild kit.
 
Almost impossible to fix a corroded bore. Try taping some 1000 grit sand paper to a suitable rod to clean out. Good luck.
 
Stephen Hill said:
Or, if you want to be really faithful to originality, you can bore and sleeve it back to stock bore size. Not the best idea, IMHO. But very doable. And you can use a readily available stock rebuild kit.
Click to expand...
I had considered that, but the 13mm sleeve kits (RGM) tap the original cylinder to 18mm. 5/8" is very nearly 16mm. I don't know what the minor diameter of the sleeve is but it doesn't seem it will leave a lot of wall thickness to play with.
 
stanthomas said:
I had considered that, but the 13mm sleeve kits (RGM) tap the original cylinder to 18mm. 5/8" is very nearly 16mm. I don't know what the minor diameter of the sleeve is but it doesn't seem it will leave a lot of wall thickness to play with.
Click to expand...
I installed the 13mm sleeve kit from Madass140 (member on this forum). It slides into stock bore and uses Locktite bearing/bushing adhesive. Works a treat. He also sells a complete modern 13mm MC that mates up to stock switchgear for very reasonable pricing. Or you can by a 13mm bore stock MC from Andover and others if you have the $$$.
 
The original bore size is not the right size for a single disc why the stock brakes are so bad, if you put a sleeve kit in no one will know and you have better braking, myself would replace the MC for a better one without kitting it, what's your life worth keeping original or having great brakes that work, I know what my choice would be, why I spent the money on a full upgrade of my front brake after my original set up nearly killed me, was a easy choice for me.

Ashley
 
If it was corrosion pitted and the stock bore size wanted to be retained for whatever reason I am sure there are folk in the UK who could bore and fit a stainless steel thin wall sleeve.

Past Parts UK maybe for one source.

Past Parts - Remanufacturing Master Cylinders, Calipers and Servos

Established in 1988 Past Parts offers both a high quality remanufacturing service and a parts service for Hydraulic Brake Cylinders, Brake Servos, and Brake Calipers for a variety of older vehicles including cars, trucks and buses, plant machinery, classic motor cycles and many other types of...
www.pastparts.co.uk www.pastparts.co.uk
 
You shouldn't even consider attempting to clean a scored or pitted Master cylinder bore.
You don't know how deep the corrosion is and how much the bore would increase in diameter to achieve a smooth faultless internal surface & the cost to have professional done would out way replacement
Replace the M/C as a matter of course
Can i ask why you have dismissed a 13mm sleeve conversion or 13mm replacement??
 
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As far as replacement is concerned, AN will supply in both 13 mm and 5/8", your choice.

Almost everyone here will tell you that the 5/8" is a bad choice, because most of us have an idea how much going 13 mm improves the brake.

So to retain original appearance, you don't need to sleeve.

The only motivation to sleeve or otherwise refurb an old bore can be to save money.
 
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Thank you all for your comments and observations which have been noted.

Perhaps I might re-phrase my question:
Does anyone have experience of using a hone, such as BC Series Flex-Hone, on the bore of an aluminium brake master cylinder, e.g.Brembo, Nissin, Magura, with a bore size typically used on motorcycles (15 - 19mm, say)?
Either as a final step after machining or, my specific interest, to renovate a used bore.

Any recommendations on abrasive type and grit?
 
stanthomas said:
I had considered that, but the 13mm sleeve kits (RGM) tap the original cylinder to 18mm. 5/8" is very nearly 16mm. I don't know what the minor diameter of the sleeve is but it doesn't seem it will leave a lot of wall thickness to play with.
Click to expand...

The master cylinder should be drilled to 16.5mm.
"ARRANGE A METHOD OF ACCURATELY AND SECURELY LOCATING MASTER CYLINDER BODY
AND DRILL 16.5MM TO THE BASE OF THE BORE OF THE MASTER CYLINDER."


Only a short section at the outer end of the master cylinder bore (where the casting is significantly wider) needs to be tapped 18mm for the sleeve thread.

"WITH OUR TAP 8 ROTATIONS IS PLENTY (MINIMUM SEVEN ROTATIONS) AND THIS
SHOULD GIVE THE 9MM OF FULL THREAD REQUIRED."

 
L.A.B. said:
The master cylinder should be drilled to 16.5mm.
...
Click to expand...
Ok, excuse my superficial and incorrect reading of the RGM conversion. But the point stands, if the O.D. of the sleeve is 16.5mm, boring to 15.875 (5/8") is not practical.
 
stanthomas said:
But the point stands, if the O.D. of the sleeve is 16.5mm, boring to 15.875 (5/8") is not practical.
Click to expand...

I've been using the RGM sleeve kit for years (and they've been selling it for years) so I can't agree that it's not practical but why would you want to bore it to 5/8" as it's meant to be used at the 13mm bore size that gives improved braking. Edit: Unless perhaps it's for double discs when 5/8" would be preferable but there's been no mention so far.
www.rgmnorton.co.uk

13MM MASTER CYLINDER PISTON WITH SEALS (USED IN OUR RELINE KIT)

025859 RGM NORTON GRIMECA 13MM MASTER CYLINDER PISTON
www.rgmnorton.co.uk
 
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