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Re-thinking my rear brake.

Discussion in 'The Garage' started by thuban, Oct 18, 2020.

  1. thuban

    thuban Horse Scratcher XS650.com Supporter Top Contributor

    Rain coming so I thought I would explore my rear brake again. The CB750 is 509 lbs dry. It has a real good rear brake, for not being hydraulic. I'm sure I could lock the rear wheel easily. The XS, it really sux. There is not that much difference between the brakes on both bikes that I can tell but I haven't matched spec to spec.
    All Jim's work and others, getting a good set of shoes, matching, centering and getting the dimple in the right direction, well if one heads over to the TECH section, the XS doesn't have a rear brake. There ain't jack. :shrug:
    My hub was smooth and not tapered and all seemed like factory. I just can't get my head around making a bike with a rear brake this bad. Under a few items, my bike is still stock and I plan on keeping it that way. The factory manual (74-77) has only a few more sentences than our Tech section along with wear limits. It would be interesting to hear what you other non-hydraulic, un-modified, rear brakers have to say?
    Might ought to hunt up Jim's and others rear brake work and slip it into the Tech Brake section because doing all that looks like the best it's gona get with the stock setup. I figured the brake would take a "set" and get better after a few miles. 1800 miles and it's still takes a good amount of pressure to tell it's doing anything.
    I drive far enough down the road, with engine braking and down shifts, I'm always light on the brakes. But If I needed all the braking I could get, and NOW, I feel I would be stubbing my toe on the pavement before I got much out of that back brake. The adjustment nut is tight as I can get it without it dragging. Shoes are just making light contact. So maybe Jim's setup is as good as it's gona get.
    GLJ and gggGary like this.
  2. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

  3. kopcicle

    kopcicle antidisestablishmentarian


    ...it is stock , kinda :) . If you ignore the kawasaki hub and the honda rotor .

    Okay , fun aside I do have a question. Has anyone ever mentioned "arcing the brake shoes" in your presence (or on the interwebz?) . Do you have an idea what I'm talking about? If not I'll continue at length and bore the hell out of everyone that has read it before :)
  4. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Just to clarify... I believe it was @5twins who's done all the work and research on the rear drum. It wasn't me.
  5. Machine

    Machine Race the wind Top Contributor

    Horse Scratcher where is your pic? Let's see what you are working with.
    This 79 adjustment is very adequate for my liking in rear braking strength.
    Paul Sutton and thuban like this.
  6. thuban

    thuban Horse Scratcher XS650.com Supporter Top Contributor

    TwoManyXS1Bs, Paul Sutton and gggGary like this.
  7. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    There was an attempt, it was not implemented....:whistle:
    Kinda like a sketchy rear brake, effort was made, results negligible.
    TwoManyXS1Bs and thuban like this.
  8. thuban

    thuban Horse Scratcher XS650.com Supporter Top Contributor

    I know how that implementation goes. I remember 5Twins and 2 many now. Don't know why I was thinking Jim, probably cause he has his fingers into everything.:laugh2:
    TwoManyXS1Bs and gggGary like this.
  9. thuban

    thuban Horse Scratcher XS650.com Supporter Top Contributor

    Machine, looks just like yours except I have a bit more adjustment rod sticking out.
    gggGary likes this.
  10. 5twins

    5twins XS650 Guru Top Contributor

    I think 2M mentioned this in that thread - if the cam was installed wrong and run that way for a long time, setting it right may not show too much improvement. The shoes have worn in with the cam set wrong. Best results will be had with lightly worn or new shoes.
    TwoManyXS1Bs and gggGary like this.
  11. thuban

    thuban Horse Scratcher XS650.com Supporter Top Contributor

    I agree 5 Twins. My brake only had a few miles on it. I had punched a dimple on my shaft when I disassembled it so it would go back the same way and noted it in my tear down book. I went out to see if there were two dimples on the shaft, mine and a factory dimple. Nope, just mine. And I would have thought I would have seen two dimples when I cleaned the parts. So, I can't tell you what way my shaft is but I can tell you for sure the shaft is installed as it came apart. I doubt anyone had ever been in that brake because brother-in-law bought it new. He didn't put enough miles on it for the brake to need servicing. It's on my list of things to check next time I have the rear wheel off.
    gggGary likes this.
  12. Machine

    Machine Race the wind Top Contributor

    Yes, you noticed.. I have gotten away with positioning the brake arm on notch more aggressive. This rear brake is the stronger than the 79 Standard of a couple years ago.
    Original shoes that are thick and low mileage. Under 7k but original I do believe.
    gggGary likes this.
  13. thuban

    thuban Horse Scratcher XS650.com Supporter Top Contributor

    I may be able to rotate my lever back and pull most of the slack out of it to get the nut on. But I want to see some threads exposed. If anything were to happen back there you would feel it in excessive pedal movement but I still want to see threads. :)
    Paul Sutton and gggGary like this.
  14. 5twins

    5twins XS650 Guru Top Contributor

    I think many came assembled wrong right from the factory, if the multitude of rear brake plate pics I've seen are any indication.

    Yes, if you have the brake arm mounted on the right spline, you'll see about 3/4" of rod hanging out of the nut .....


    I think Machine's is one spline off.
    TwoManyXS1Bs, Paul Sutton and gggGary like this.
  15. thuban

    thuban Horse Scratcher XS650.com Supporter Top Contributor

    Yep, that's what I have. I think Machine positioned his like that on purpose. More mechanical advantage? I don't know.
    gggGary and Machine like this.
  16. aldo5468

    aldo5468 Redleg XS650.com Supporter

    For awhile some years back, I had midset controls on my '82 - if you think that rear brake action is marginal with the OEM brake arm, try one that's about half as long! Went back to stock!

    Attached Files:

    Paul Sutton, gggGary and thuban like this.
  17. Machine

    Machine Race the wind Top Contributor

    True, it is "one spline off". To get there I cheated slightly. The adjuster nut radius was pretty buggered up so I used a regrind 1/2" endmill to carve the radius out deeper than original. This fit the rod pivot nicely. The threads on the rod are just shy of the end..
    Maybe it does not matter in "mechanical advantage" but it seems to. Besides, sometimes I do whats "wrong" often just to look better or better yet.. sometimes work better.
    thuban and gggGary like this.
  18. Hudriwudri

    Hudriwudri XS650 Member

    Hi there,

    I really like the setup!
    Does the kwaker hub have a cushdrive?
    If so would you be so kind what model the hub is of and what was involved mounting it, as I'm looking for a semi easy "affordable" to mount (Hub width and axle diameter) disc brake wire wheel rear hub.

    Thanks and kind greetings

  19. kopcicle

    kopcicle antidisestablishmentarian

    The rear caliper is bone stock 2F0 . I was careful to leave as much of the conversion stock as possible . With the un-modified KZ750B LTD M1 twin 18" disc brake hub and rim the Honda disc centers in the caliper once .200" is taken off the diameter . Now one caution , the disc was "marked" CB200C but I did not take it off myself so I won't swear to it . I'm told that the KZ305 is very similar also so ya pays yer money and takes yer chances . I did turn down one side of the rear hub and I believe it was the sprocket side . Simply put it was either the center of the the sprocket or disc that was too small by an annoyingly small amount. I mounted a rear axle in the drill press plate and aligned it with the spindle. A 1/4" end mill trimmed the diameter. Crude but effective. As the project stands the disc is centered in the caliper and the sprockets are so nearly in alignment that I may be able to let it go . I did have to futz with spacers for hours but it fits . I should say almost fits . I'll have to pull the wheel toward the drive side about .250" to put it on center line but with all else falling into place I'm far beyond complaining. It will take a talented wheel builder to sort this out as it's a cone type center hub and the spokes will have to be hand cut and threaded. I had considered the modification of the front hub to carry sprocket and disc but going without the dampener was more than I or the gearbox and transmission could tolerate .

    thuban and gggGary like this.
  20. xjwmx

    xjwmx It's just the unknown. Top Contributor

    You don't want a good rear brake, really. Get up to about 35 or 40 in a parking lot and slam on both brakes like an emergency stop. As the weight transfers to the front tire and comes off the rear, the XS rear will lock up too. You never want the rear to lock up, lose traction, and try to get in front of the front by sliding sideways... Better to practice stopping than fix a brake that ain't broken.
    thuban and gggGary like this.

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