Honda 1973 cb350 caliper

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?

 

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...

 

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
dangerous....

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!

 

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
c-clamp.

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 www.bikebandit.com

Click on OEM > Honda > 1973 > CB350G > brake caliper

 

That would be the main caliper mounting bolt.

Wrong again.

 

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?

 

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.

 

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 www.bikebandit.com 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.

http://www.cyclemaintenance.com/mechicscorner/cb750_brakes.htm

 

Attached to, via a lug

Indeed.

 

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...

 

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.

 

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?

 

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.

 

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?

 

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
frequently.

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
engines......

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.

 

Sounds like a lifetime job for you then, Mr. Sisyphus.

 

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.

 

Or, much more likely, they don't realise that a lot of it is rubbish.

 

Without the Greek characters:

Autik epeita pedonde kulindeto lais aneides

If you're trying to be literate - consider that others are, too.

 

An intellectual may free-associate endlessly as a pastime, but his
motivation is still the same as a gorilla's.