Front brake refurbishment/upgrade contemplations...

[XSLeo]

Basically. It has much to do with lever ratios as well as the area of the M/C piston.
If the lever raio remains the same and the bore size gets smaller the pressure increases. Say with your 16mm bore with a 4 to 1 lever ratio, you pull the lever with 25 pounds, this put 100 lbs on the piston. Changing the lever ratio can have a simular effect. Going from the 4 to 1 to a 5 to 1 would increase the 25 lbs on the lever to 125 lbs on the piston. Changing the lever ratio might be harder than bore size.
Just pulling the lever out toward the end can change the way it feels. In a regular grip your index finger is about a 1 to 1.5 ratio, moving your grip out can change it to a 1 to 3 or 1 to 4 ratio. I should go measure a lever and see just what the ratio is. From the pivot point to where the lever pushes on the piston is about 1 inch. From pivot point out to your index finger is about 2 inches.
This will chage the numbers but moving your hand out so you use more lever will change things. Same when pulling the clutch.
The 16 mm piston has about a 200 square mm's area. This will give you 50 lbs per 100 square mm in the line.
A 14 mm piston has about 153 square mm area. So your putting 65 lbs per 100 square mm.
These numbers are not actual tested numbers but just to show the difference.
This shows you the dropping the bore size does increase line pressure. This increase does make the caliper squeeze the pads to the rotor harder for the same finger pressure. This increases the strength of the brake and increases the feel at the lever.
Going smaller on the bore size increases the lever travel . Going too small can increase the lever travle enough so the lever could hit the grip before the brakes work. This would have to be an extremely small bore size, not likely with most brake caliper to M/C sizes but a possibility.
Leo

 

[TeeCat]

Leo, this is great information to have... thanks for taking the time to write this. Even if I end up staying with a stock M/C, this would be a great project, and is really a great candidate for the in the "How To" section, I think! I'd love to try this if I had the wherewithal and didn't mind having my bike out of commission for a while.

TC

 

[XSLeo]

Once you get the caliper cleaned out or rebuilt, the only down time you would get is the time it takes to swap the M/C's and bleed the brakes.
Getting an assortment of M/C's might be the tricky part.
One thing, after the experementing you can sell off the ones that you don't use and maybe at a bit of profit, enough to cover the cost of the one you use.
Other brands of bikes used a M/C that looks like the XS650 M/C, You might find one that very closly resembles your stock M/C but be a smaller bore.
Leo

 

[TeeCat]

Once you get the caliper cleaned out or rebuilt, the only down time you would get is the time it takes to swap the M/C's and bleed the brakes.

Yeah, but you have to remember that even seemingly the smallest tasks just take me forever because I tend to be hyper-cautious, especially with something like brakes. I also tend to be a bit of a perfectionist, which can really get inconvenient. When I'm ready to bleed this brake (or whatever else I end up doing to it), I'll have to look up all that to prepare, because I have not bled a brake in about 30 years. So it will be like starting all over again and re-learning it all.

TC

 

[PetesPonies]

Did you get your brakes updated?? We need to meet this summer . . maybe up in your area. Its a nice ride up there.

 

[PetesPonies]

TeeCat . any chance to meet and talk?

 

[TeeCat]

Hi, Pete! Not sure how I missed your post.

No, not yet, sir... I'm waiting for parts. I ordered the M/C from Mikes that you asked about in another thread, plus some replacement hoses and a rebuild kit for the caliper. I'm a little apprehensive because I have never done this before, but I want to do it myself. Doing some research in the meantime.

We definitely need to meet up. I'm in Ellicott City. I also want to ask you some things about my tubbed '85 Mustang GT as well. I have not run it in about 4 years, and there is a nice crease on the right door and front fender that I did when I first got my little Ninja (butt end of a mirror). I'm retiring next year, so if I keep it, I need to find someone who can do good body and paint and help me get it running again. She's untagged now.

But I want to get this front brake done right, and fast, so I can ride my TX some more this season now that she has been increasingly cooperative.

TC

 

[CDNTX650]

#08-0265 is the M/C i used form mikes on my 74. Caliper rebuild/new pads all new rubber/hard lines and it feels pretty damn good for what it is.

 

[TeeCat]

Yup, I'm gonna use #08-6009 and rebuild the caliper, and replacement stock hoses. Oh... I have to get a bleed kit too, I guess... or some tubing and a bottle.

 

[scott s]

I've been searching and reading through numerous threads and I still have some questions...

I have a '75 with the early style m/c and 2 piston caliper. The brakes were horrible. Very spongy and weak.

Rebuilt the m/c and the caliper. No change.

I added stainless lines and a master cylinder from David Silvers Spares (it's a Honda m/c but has the same look as the early style, round reservoir XS m/c's. This was before Mikes started offering the early style). Better, but still soft.

I believe the David Silvers m/c is the same bore as the stock XS. It appears I'd have better luck and a firmer feel if I went with a smaller bore m/c, but I'd lose that stock look.

I do have another caliper that I could use to convert to dual discs. Would that make the ~14mm master cylinder feel better?
Do you think maybe I could have a problem with the caliper and not the m/c?

The brakes are functional, but nowhere near as good as the late model stuff on all the other XS's I've owned.

Am I doomed to run the modern looking 12mm m/c on my otherwise stock appearing bike?

 

[PetesPonies]

Your '75 ( as mine also ) should have a 16mm MC as stock. If you have a 14mm now, you are getting a benefit from increased pad pressure albeit with slightly more stroke needed. I went with a 13mm , still hasn't arrived yet. It won't look stock, but that's not important with my bike. I have a Honda ,I believe, on there now. I do not know teh size of the piston, but braking sucks.

 

[musicman]

Leo, thanks very much for all this additional information. For a brake neophyte like me, it's a lot to digest! Sifting through it several times, though, and considering what you have said about the various M/C sizes, I think I'm actually more concerned about just knowing the state of repair that the system is in than I am about changing the feel of the lever. All things considered, I'd like to stay with as close to stock M/C and caliper as I can - basically replace each of them with a new unit - but go with one stainless hose, eliminating the junction. If this basic plan would be okay, what additional fittings (bolts, washers, etc.,) would I need to complete the picture? I suppose that either you or Travis could tell me what particular hose to order, though I'd have to measure. And I suppose the banjo bolt at the M/C should swivel, right? And if I eliminate the junction block, I'd just use a loop of some kind to keep the hose close to the lower triple tree, right? I don't have the bike in front of me... sorry...

By the way, here is my brake switch, which I would like to keep:

Thanks again, Leo!

TC

Hey, if the parts fit from Mike's I would jump on them. The price is great and the parts are new! I have a problem with my 1972 XS2, and nobody knows if the stuff Mike's has will fit, so I think I might order them and try. Right now, I have no front brake

 

[PetesPonies]

Your '72 has the same brakes as the '75.

 

[aReJay]

XSleo, you just answered all my front brake questions in one post! thank you very much!

 

[raptorhertz]

Bumping an Old thread!
I have 1975 front master cylinder, I thinking of doing a rebuild of it as it has not been used for long.
Yamaha offer a MC rebuild kit:-1A0-W0041-00-00, cost around 88$.
Mikexs has listed a kit:-http://www.mikesxs.net/product/08-6010.html can this be used on the OEM caliper or the listed kit is specifically for MC(76 style) offered by MikeXS 14$http://www.mikesxs.net/product/08-6009.html

 

[jd750ace]

650 Central accepts PayPal. All you need is a PayPal account and E-mail addresses.

 

[raptorhertz]

650 Central accepts PayPal. All you need is a PayPal account and E-mail addresses.

I am keen to know that $14 MC rebuild kit will serve the purpose of rebuilding the OEM MC or the kit is good for after market MC listed my MikeXs(link added)

 

[XSLeo]

All the M/C's from 72 to 76 were 16 mm bores. So that kit, #08-6010 that fits the M/C # 08-6009 should fit your stock M/C. I say should because they are the same bore size. I haven't used that rebuild kit, so I can't say for sure it will fit.
Leo

 

[raptorhertz]

All the M/C's from 72 to 76 were 16 mm bores. So that kit, #08-6010 that fits the M/C # 08-6009 should fit your stock M/C. I say should because they are the same bore size. I haven't used that rebuild kit, so I can't say for sure it will fit.
Leo

Thank You Leo! Given an option between two, which one should I opt for? Its matter of brakes, 70$ may make big difference in the end. Can't take chances here!
Somehow I feel, the kit won't work on stock MC. It's made for replacement MC.
offered for odd 15$, he should charge around 35ish for same,lol.....
Perception- Low price- cheap QC

 

[XSLeo]

I somewhat agree with that. Sometimes cheap is not the best way. Brakes are pretty important.
On somethings cheaper is ok, like if you search for a specific thing on ebay, getting it the cheapest is ok. As long as it's the same thing.
Like putting Dunlop D401 front tire in the search then picking the price that's lowest.
Just putting front tire in search and picking the cheapest may not get you a good tire.
Leo