1973 850 front brake master cylinder.......

Looking to keep my original lockheed master but found out it was pitted inside...have already purchased a stock rebuild kit and piston....do not want to upgrade to the smaller bore so.....do I just keep looking for a serviceable master core?...any other options?...

Well, the sleeve to a smaller bore is a standard way to both fix the pitting and improve braking on the OEM master cylinder but you specifically stated you don't want to do that. Are you wanting to keep it totally stock for resale or other reasons? Does it have to stay on the bike? IOW, would keeping it on the shelf in the garage be an option while going with a different MC? CNW's Brembo MC can be mounted to the original switchgear with their adapter plate and will make the front brake act like a modern one as far as feel/stopping power. Of course the Brembo MC does not look stock so if the bike must appear stock and a resleeved MC is not to your liking, then the only option is to find an old one in good condition. Does Norvill carry "new" ones?

An original with intact bore is going to be quite the search. Here in the Boise valley where the humidity rarely gets above 20% in the Summer, my master cylinder still corroded to the point that the fluid would run out from the piston bore. You can have it sleeved, have a better brake, and no one would ever know the difference without disassembly.

'Curious as to why not upgrade to smaller bore. Between the poor hydraulic ratio and chrome-plated disc, it takes two men and a boy squeezing on the lever to get the old girl to stop.

Nathan

Here's an old one for $15 that includes the lever and bolt. Seized up, but maybe the bore is intact?
https://www.ebay.com/itm/Lockheed-D...ash=item48a6b07cfb:g:Fe8AAOSwv-ZaRX05&vxp=mtr
For that money, ya can't go wrong, seein as how the brand new one is about $250.

Keep in mind that yours COULD MAYBE be saved with fine paper (600 grit?) hone and polish, and that the bore is not the only wear point here. The threads for the brake switch or the hose can get buggered, the outer bore can get scraped often by the star washer until it's too big also.
Here's a recent thread
https://www.accessnorton.com/Norton...linder-and-caliper-rebuild-with-photos.24231/

Like others have mentioned, you might wanna re-think the idea of original 5/8 bore idea being desirable. All by yourself in a great big world?

Any decent machinist will be able to bore it out and sleeve it back to stock ID. Then you can use your rebuild kit and keep it stock.
At the risk of being blunt......... this will cost you more than getting it sleeved down in size and it will still be a crappy brake.

Stephen Hill

Old Britts shows this as available:
14-061939/13 Master Cylinder, Complete kit, 13mm, Pre-1975 1 - 355.00

Thanks for the replies guys....my reason for stock is that I like the original look..and I already have all the parts.The bike will most likely be resold in the spring and money is a factor...I have heard people say with the smaller rebore the front brake can become too touchy?....just trying for a cost effective solution as I still have a fuel tank to "unseal" and recoat..tires...etc...Thanks mr. rick for the ebay lead...I will watch...

keso said:

...I have heard people say with the smaller rebore the front brake can become too touchy?

Click to expand...

I have not heard that as a concern on the antique single disc front brake. With a 1/2" bore, upgraded Ferodo pads, and the disc Blanchard-ground, the brake is now a very controllable and usable two-finger operation. Besides, I would be inclined to think that that would be a great selling point!

Nathan

Best I've had on Peel, matches above, 13mm sleeve, RGM race lever, SS braid hose plus taking lots of mass out of the locomotive like rotor. Mainly gave quicker easier to squeal effort/control a 110 tire so feels more powerful secure but not much shorter slowing than just removing factory restriction with stronger fear grip.

BEAWARE some resleeves or new ratio lever can allow surprise automatic lock up/no release when fluid heated expanded by sun or heavy use. Solution is sand piston or lever contact to let piston retract a few 1000th more or til don't hydrolock with heat.
If sensing fading after heated ride testing likely still tiny bubbles adhering to hose walls to bump loose to bleed better.