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post #1 of 8 (permalink) Old 10-14-2019, 04:50 PM Thread Starter
Grand Prix 250
Main Motorcycle: 1977 T140V
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To rebuild or not to rebuild

Hi all,

Last time I had the 77 T140V out the rear brake locked up. I had gone through standing water earlier on the ride, high enough that it may have submerged part of the caliper, but probably not the master cylinder. It was about 30 min later that I had it seize up, in stop and go city riding on a hot day. I was able to pull over and after pulsing the brake pedal about a dozen times got it unstuck. Made it home without incident. I'm not sure if it was the caliper or master cylinder or even just water in the lines that caused this. On a subsequent ride today I was unable to reproduce this.

Starting to plan winter maintenance. Should I be thinking of rebuilding the master cylinder and/or caliper? Not sure the last time it has been done. Or should I just flush the lines and not worry about it unless it happens again? Likewise for the front brake, which I've not had any issue, is it a good idea to periodically replace the seals in the master cylinder, or if it ain't broke don't touch it and just flush the brake fluid?

Thanks,
Neal.
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post #2 of 8 (permalink) Old 10-14-2019, 05:06 PM
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You don't say what work if any has been done to the brakes in the past

A few years ago I replaced my master cylinders with stainless ones, and rebuilt the calipers with stainless Pistons. I also replaced the hoses and used DOT 5 fluid

You can't mix fluids as they don't mix

The original hoses only last 10 years before delaminating and becoming one way valves.

If you have the time and money and the bike won't be laid up when you want to ride, go for it
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post #3 of 8 (permalink) Old 10-15-2019, 06:58 AM
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Hi Neal,

Both front and rear brakes' hydraulics are closed systems. So, unless either system is leaking fluid (in which case you should be rebuilding the offending system), water cannot possibly have entered the rear brake hydraulics.

As Dave posted, you haven't posted whether other work's been done on the rear brake or rear wheel recently. If it has, check that first to ensure the problem you're posting about wasn't caused by that work. Otoh, if no work has been done recently on rear brake or rear wheel, +1 to what Dave posted, ime and mho, the complete system needs stripping. cleaning and inspecting; not difficult just a bit time-consuming - AP Lockheed manual.

If the hoses are more than ten years old, or you don't know, be aware that none of the remaining parts of "Lockheed" make new hoses, they're all pattern parts. However, fwiw I haven't used even Lockheed-made hoses in over thirty years, I prefer to make my own from Goodridge braided - easy to do if you can wield a hacksaw or Dremel and spanners. Then you never have worry about the "delamination" nonsense and it's easy to incorporate proper brake lamp pressure switches (as even Meriden did on the front '79-on ).

Hth.

Regards,

Stuart
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post #4 of 8 (permalink) Old 10-15-2019, 09:22 AM Thread Starter
Grand Prix 250
Main Motorcycle: 1977 T140V
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Thanks for the replies.

re: previous work on the brakes. Last year I replaced the pads and had the rotor resurfaced, front+rear. I made it through a season of riding without issue (pads are wearing evenly), so I'm not sure if the current issue is related.

I don't know the history of the brake systems prior to my obtaining the bike about 5 years ago. I replaced the rear brake hose about 4 years ago as it was damaged. It is till the Lockheed calipers and master cylinders, and not sure if they have ever been apart. I'm intrigued by the stainless option -- although it is quite expensive -- is this overkill though for a bike that is only ridden on the weekends?
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post #5 of 8 (permalink) Old 10-15-2019, 03:34 PM
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There are plenty of t140's running on original brake parts and (hopefully) new hoses
But personally bikes are more of a hobby than a transport system these days. I've owned the bike since 84 and will keep it till I drop off my perch. I don't mind spending cash on what might be seen as a luxury

When I tried to service my master cylinders they were so hard to disassemble that I just bought stainless ones
You don't need to do it all at once - so long as you enjoy bleeding brakes.

I also have a back hydraulic switch to go on at some point because the original is bloody terrible
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post #6 of 8 (permalink) Old 10-16-2019, 01:23 AM
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Main Motorcycle: 1973 Triumph TR7RV
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Hi neal77bonnie, I know many rebuild the master cyl. I don't know the condition they were in. I don't have a lot of experience, but every Triumph caliper I've been involved with was rusted in the area where push rod/piston ride. So the seal cup was riding partially on rusted surface. Deeper in cyl was fine. This area takes a lot of water & after honing would rust even faster.

For that reason I just replace with new LF Harris stainless master cyl. All have worked quite well & lasted well. Mine has been on for almost 6 years now & no seeping & works good.

The caliper is a different situation. If the groove the piston seal rides in is not rusty the rebuild kit should work good. If piston is rusty replace it. Stainless piston is good choice here also, but new steel is fine. Rust inside caliper body should be removed, but unless pitting is bad it often will work good with new pistons & seals. Again the groove for seal must not be rusted or pitted.

Since rubber hose is only 4 years old, replace it or not. In any case inspect it & test for blockage. Same with steel lines. Sometimes still lines are very rusty inside. Replace as needed. Often they are good.

4 things cause the brakes to stick on.

Least common is stuck caliper pistons.

Common is brake hose collapsing inside. Pressure forces through when applying brake, but the caliper piston seals cannot force brake fluid back to master cyl. So pads are still pressing on disc.

The next 2 things are the brake pedal doesn't return all the way which doesn't allow the piston in master cyl to uncover fill port so fluid can't flow back into reservoir. Along the same lines the master cly isn't adjusted on its threads properly. So the port is again covered by the piston not allowing the fluid to return properly, holding on the brakes. Often either of these 2 it works ok at first, but with riding the fluid warms & expands applying breaks.

The master cyl depth adjustment of the threads is very complicated until you learn exactly what to look for/at. Once you understand what you need to achieve it's very simple.

Before installing new or rebuilt master cyl I recommend you practice the adjustment with the old master cyl. Study the instructions as you do it. On purpose mis adjust it & see how it effects the piston position in relation to the fill hole.

From your description & since you hose is only 4 years old, my hunch is the adjustment of master cyl thread depth was on the edge of tolerance & the pedal may not have been returning 100%. Again just a hunch. Working pedal may have brought things back.

Are you sure there is not signs of seepage inside push rod boot?

If calipers are sticking I've not found pumping pedal usually frees them. It might help slightly, but still tend to drag & get brakes hot.

I've seen several collapsed inner linings on brake hoses. Pumping brakes is crap shoot. Sometimes will free it for short time. Sometimes not. Sitting a while will often drain back fluid slowly so ok for a short while.

Certainly nothing wrong with doing it all.

The thing is if you do 100 miles or 5000 miles a year doesn't matter. When you need the brakes to work, you need them. They say most collisions are less than 5 miles from home. Good brakes are not a luxury. A necessity!

Let us know what you decide & how it turns out.
Don
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post #7 of 8 (permalink) Old 10-16-2019, 05:52 PM Thread Starter
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Great advice all. I'm leaning towards the stainless option just to have peace of mind. Don't want to skimp on the brakes, especially since I'm running stock discs and pads.

Did you just replace the barrel assembly:
https://thebonnevilleshop.com/triump...7a-99-9918s-1/

Or the entire master cylinder assembly:
https://thebonnevilleshop.com/triump...-pn-60-4401-s/

Will do the same for the front brake, and while I'm at it, rebuild the caliper as well with stainless pistons and fresh seals.

Neal.
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post #8 of 8 (permalink) Old 10-16-2019, 07:08 PM
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Hi Neal,

Quote:
Originally Posted by neal77bonnie View Post
I'm leaning towards the stainless option
Did you just replace the barrel assembly:
Or the entire master cylinder assembly:
Ime, 'fraid this can't be pre-planned, depends what you find when you dismantle.

Worst-case, you find whoever worked on either master cylinder last didn't grease either the locking grub-screw or the master cylinder thread into the ally mounting casting, and these are now corroded together; if any fluid has leaked from the master cylinder, the corrosion'll be even worse. Note it isn't always impossible to separate the parts, I've had 'em separate with only moderate force after only being submerged for spark-erosion of the grub-screw. However, I didn't have to travel very far to the company doing the spark-erosion ... if you do, it might simply be cheaper to pay for a complete new master cylinder, with both stainless cylinder and piston.

If you do buy either a complete new assembly with both stainless cylinder and piston, or just a new stainless cylinder - as they also aren't made by any part of "Lockheed" - ime I advise against simply assuming it's a bolt-on assembly/part ... faults I know of on pattern stainless master cylinders:-

. cylinders not honed after ports to reservoir drilled - sharp edge of holes inside cylinder nick seal;

. neither master cylinder-to-mounting thread nor locking grub-screw greased;

. master cylinder not adjusted correctly in mounting - Lockheed manual;

. locking grub-screw not stainless ...

Quote:
Originally Posted by neal77bonnie View Post
Will do the same for the front brake, and while I'm at it, rebuild the caliper as well with stainless pistons
Plus braided hoses with stainless end fittings replacing both steel pipes and unknown-age rubber hoses? I appreciate not cheap but fwiw the first first braided hoses I made well over thirty years ago are still indistinguishable from brand-new.

Hth.

Regards,

Stuart
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