Honda 1973 cb350 caliper

Discussion in 'Motorbike Technical Discussion' started by Ig, Mar 17, 2007.

  1. Ig

    Ig Guest

    Well, the bike is sweet but needs some work. and of course, all those
    "easy fixes" never turn out that way. Here's the first problem, hoping
    you fine people can help...

    I have a jammed brake pad in the front caliper. took it of to take the
    thing apart but the pad seems to be completely locked in. I am
    assuming that there is a piston behind this, but can't even get to it.
    I will try to pry it out tonight with some needle nose plyers or
    something... is there a "mechanic's trick" to this (a couple of whacks
    with a hammer)... or is this highly uncommon and need to look into
    getting a new caliper altogether?
    Ig, Mar 17, 2007
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  2. Ig

    Ron Seiden Guest

    Assuming that you've unscrewed the bleed screw to drain any brake fluid (if
    you haven't removed the bleed screw, the piston would be held in by air
    pressure/suction), then you might want to try & trickle some Kroil into the
    cylinder (through that bleed hole). Let it sit for a couple of days & the
    Kroil will break up most rust &/or corrosion that may be jamming the piston.
    Then tap on the face of the brake pad to break loose the piston.

    If the pad is rusted onto the front of the piston, trickle some Kroil around
    the pad...
    Ron Seiden, Mar 17, 2007
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  3. If it's the pad behind the piston (the bigger part of the caliper),
    simply pump the brake lever. If you've dismantled the brake system, then
    attach a grease gun to the line and use hydraulic pressure there.

    Using compressed air also works, but the results can be spectacular and

    If it's the fixed pad, they can be right sods. Do check that it hasn't
    got a little split pin at the back of the caliper - some are secured
    like that. Otherwise, soaking it in paraffin (kerosene) for a couple of
    days should do the trick. Do not attempt to e-use the pad after this!
    The Older Gentleman, Mar 17, 2007
  4. It's a single-sided caliper, with one piston on the outside pushing
    the one brake pad and the other (dead) side just has a
    brake pad attached to it.

    Putting pressure on the piston pushes the "live" pad against the brake
    disk and the "dead" pad is pulled toward the "live" side.

    Don't laugh. Most cars have single-sided calipers that work that way,
    and the mechanic must remove the caliper and
    pad and push the piston back into its bore by using a large

    But Honda seems to have designed a piston retractor jack screw into
    the pivoting caliper arm, from what somebody once told me...

    The whole caliper is mounted on a rather long pivoting aluminum
    casting and there is a mysterious crosswise bolt in that arm.

    I had just helped a friend replace his brake pads by prying on the
    pad's iron backing plate with a screwdriver to retract the piston on
    the live side, and I was pumping up the brake pressure again, when a
    wise guy who owned a CB-750 told me that I didn't need to use a
    screwdriver, because the crosswise bolt was intended to retract the
    piston when tightened...

    There is a diagram of the brake caliper on

    Click on OEM > Honda > 1973 > CB350G > brake caliper
    Potage St. Germaine, Mar 17, 2007
  5. That would be the main caliper mounting bolt.
    Wrong again.
    The Older Gentleman, Mar 17, 2007
  6. I see two bolts in the diagram that appear to hold the caliper to the
    pivoting arm and a single longer bolt with a spring on it.

    What is the spring for?
    Potage St. Germaine, Mar 17, 2007
  7. Ah. I was thinking you were referring to the larger bolt in the same
    plane, that holds the caliper to the fork leg.
    You figure it. I've owned maybe 15-20 bikes with that caliper, and it
    isn't hard to work out.
    The Older Gentleman, Mar 17, 2007
  8. A bloody lot of help you are, ya cheeky bastard.

    The spring seems to hold pressure on the caliper adjusting bolt to
    keep it tight.

    I never owned a Honda with disk brakes so I've never had to adjust the
    front caliper to keep it from squeaking and binding.

    I can't make out from the diagram on exactly which
    two holes #11, the caliper adjusting boltgoes through, but I suppose
    the head of the bolt is going through the fork slider.

    The concensus of opinion on Honda forums is that you can ride a Honda
    for years without the caliper adjusting bolt.

    Here's a website where the guy had to take his front caliper apart
    because the piston was stuck.
    Potage St. Germaine, Mar 18, 2007
  9. Attached to, via a lug
    The Older Gentleman, Mar 18, 2007
  10. OK, now that we are both tuned to the same channel, doesn't it seem
    likely that tightening the caliper adjustment nut several turns, and
    then loosening it the same number of turns would force the piston back
    enough so you can pull the live brake pad out of the caliper?

    Maybe Honda didn't intend the caliper adjustment bolt to be used as a
    poston compressor, maybe the guy that told me it could be used in that
    manner was just a natural mechanical genius...
    Potage St. Germaine, Mar 18, 2007
  11. FFS.

    Have you seen the spring? It would disgrace a Biro.

    Have you see the threads in the lug on the fork leg? The sort of force
    needed to push a piston back would strip them in a very short time.

    Have you twigged that it's not an adjustment nut at all, but actually a
    screw with a slot in it, that you turn with a screwdriver. The nut is
    just a locknut. You try using it in the manner you describe and see how
    far you get.

    Finally, turning the adjuster in the manner you describe is opnly
    possible when the brake is fully installed, and you can't pull the pad
    out because there's the disc on the way.

    You want to push the piston back and extract the pad - remove the
    caliper and use a G-clamp.

    The bloke who told you it was a piston compressor was, like you, talking
    out of his arse.
    The Older Gentleman, Mar 18, 2007
  12. Whatever in your Islands of Mediocrity is a "Biro"? Do I really need
    to know?
    No, I never paid that much attention to Hondas, except when Honda
    riders begged me to help them fix their ersatz motorbikes.
    Should I be humbly grateful to another arsehole for straightening me
    out on that trivia?
    Potage St. Germaine, Mar 18, 2007
  13. Google is your friend. You use Laszlo Biro's invention every day.
    OK, so you've postulated *another* load of crap, had it shown up for
    what it was, and resorted to sneering instead. Fair enough.

    What this has shown is your ignorance. Well, no matter. There's nothing
    wrong in ignorance. I'm ignorant of many things. But I don't expound on
    them as though I'm well-versed, because that way lies ridicule.
    The Older Gentleman, Mar 18, 2007
  14. Only from people who have nothing better to do with their time.

    I have an idea. Let's agree that you enjoy disagreeing
    for the sake of being disagreeable

    Fair enough?
    Potage St. Germaine, Mar 18, 2007
  15. No. Now read this carefully.

    This is not me disagreeing for the sake of being disagreeable. This is
    me disagreeing because what you've posted is arrant nonsense. I mean,
    saying that a brake adjuster can be used to help remove brake pads....

    Just recently, in another thread, you accused me of taking an unfair
    stance against Germans and being generally racist (though you didn't use
    the word).

    I pointed out that you had attributed someone else's remarks to me: that
    you'd misread the thread. As you had.

    The standard thing to do here is acknowledge your error. An apology is
    nice, but not essential.

    You did neither. You just quit the thread.

    You do this *every* time you make an error, which you do quite

    How about when you told some guy with a Ducati 800SS that his battery
    was located behind the fairing? I pointed out that in fact, it's under
    the tank. Had he taken your advice, he'd have been ripping his fairing
    apart for no good reason.

    And I won't repeat your endless howlers when we were discussing diesel

    Everyone makes mistakes. On a technical forum, one should expect them to
    be highlighted. When I make mistakes, I have no objection to them being
    pointed out, and I try to acknowledge my errors.

    When you've posted something true and accurate, you'll often find me in
    agreement. But take the rough with the smooth.

    In other words, accept that you *don't* know everything and that much of
    what you do post is incorrect.

    Your current behaviour shows you in a very unfavourable light, as other
    posters have noted.
    The Older Gentleman, Mar 18, 2007
  16. Sounds like a lifetime job for you then, Mr. Sisyphus.
    Potage St. Germaine, Mar 18, 2007
  17. Since the newbies rarely complain, I believe that the free help I
    offer is useful to them, or that they don't read it at all because of
    short attention spans.

    People with short attention spans tend to make mountains out of
    molehills anyway.
    Potage St. Germaine, Mar 18, 2007
  18. Or, much more likely, they don't realise that a lot of it is rubbish.
    The Older Gentleman, Mar 18, 2007
  19. Without the Greek characters:

    Autik epeita pedonde kulindeto lais aneides

    If you're trying to be literate - consider that others are, too.
    The Older Gentleman, Mar 18, 2007
  20. An intellectual may free-associate endlessly as a pastime, but his
    motivation is still the same as a gorilla's.
    Potage St. Germaine, Mar 19, 2007
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