Restoring & Modifying 1971 OIF TR120

[NM Bonny]

It was not corroded at all. Check out this AP Lockheed Service Manual note which declares master cylinders after early September 1977 are not serviceable. Real cool, huh? Mine is a November 1977 make, and let me tell you, I destroyed the thing TRYING to get it apart:

Well, those buggers…

 

[Lordmac]

That said, I replaced the standard mixture of steel pipe and rubber hose between master cylinder and caliper with a single piece of Goodridge braided hose (incorporating a proper hydraulic brake switch to replace the mickey mouse mechanical switch by the lever). Rear disc brake bleeding is a lot easier ...

Now this interests me considerably. I always thought the rear caliper should have a chrome cover like the front one, but because of the steel "s" pipe, the cover will not fit. And, the idea of a "one-piece" braided hose sounds significantly more robust with less clutter and fittings than the original rubber-covered one with the steel pipe. I wonder if a cover could be used with the new setup?

 

[Rudie]

You could not service the rear master cylinder because it was corroded?

It was not corroded at all. Check out this AP Lockheed Service Manual note which declares master cylinders after early September 1977 are not serviceable.
I destroyed the thing TRYING to get it apart

Did you find anything other that corrosion that prevented you dismantling the original rear master cylinder? I and others on forums have serviced dozens of them over the years, if lots of September 1977 onwards Lockheed master cylinders really could not be dismantled, it would be all over the forums.

Ime, corrosion is the killer, especially as these bikes get older and original master cylinders remain untouched for longer. I have yet to be defeated dismantling an original master cylinder but, in addition to various heat sources, I have access to specialist removal like spark erosion. Nevertheless, having dismantled an original master cylinder, I am finding more and more new parts are required, to the point where a complete new master cylinder is often cheaper and less time consuming.

I replaced the standard mixture of steel pipe and rubber hose between master cylinder and caliper with a single piece of Goodridge braided hose

I always thought the rear caliper should have a chrome cover like the front one, but because of the steel "s" pipe, the cover will not fit. And, the idea of a "one-piece" braided hose sounds significantly more robust with less clutter and fittings than the original rubber-covered one with the steel pipe. I wonder if a cover could be used with the new setup?

As standard, T160 rear caliper has a chromed cover same as the front, original T160 rear steel pipe did not prevent the cover being fitted. Replacing the original steel pipe and rubber hose combination with braided hose, a more expensive hose end fitting (90 degree female on to a male/male adapter into the caliper) was needed to retain the cover. When I replaced the original steel caliper with an alloy one, as the chromed cover does not fit the alloy caliper, I was able to use a cheaper banjo and bolt.

 

[Lordmac]

Ime, corrosion is the killer, especially as these bikes get older and original master cylinders remain untouched for longer.

I can't really argue that point. As this machine has been stored in a dry environment and not exposed to any moisture directly, corrosion has not been much of an issue. However, I realize INSIDE of the master cylinder is a whole nuther issue. The only way I could see if it was corroded (though externally there was no indication of such) was if it came apart and could be examined. It did not come apart. It is so glued together no evil and mean twisting could make it budge. So, in lieu of that, I replaced the master with Harris's stainless model. Very nice too. But still, there is something amiss, and I SHALL get to the bottom (literally) of it! And, if I wanted to, I could buy an old-stock replacement that DOES come apart.

 

[Rudie]

As this machine has been stored in a very dry environment and not exposed to any moisture directly, corrosion has not been much of an issue. However, I realize INSIDE of the master cylinder is a whole nuther issue. The only way I could see if it was corroded (though externally there was no indication of such) was if it came apart and could be examined. It did not come apart. It is so glued together

One thing that does that is any of the glycol based brake fluids (DOT3, 4, 5.1) if the seal at end of the cylinder inside the mounting leaks. It is also possible leaking fluid is the necessary electrolyte for that type of corrosion between master cylinder and mounting casting? I first took my bikes' master cylinders apart decades ago, greasing any threads during reassembly and swapped to DOT5.

If the "glue" is congealed old brake fluid, and you have access to spark erosion, one thing that might break the bond is overnight or so in the liquid in the tank.