Honda caliper - that was odd

The buyer of my recently eBay'd CB550 turned up, with a mate, to collect
the bike.

Fifteen minutes he was back, not a happy bunny. The front caliper had
seized up and you could hardly push the thing.

OK, so the piston was free and the swinging arm was free, and it had new
fluid in it - I know, because I did all these things.

So I undid the two bolts that hold the caliper halves together, cracked
the bleed nipple, and pushed back the piston with a G-clamp, and he
could see it went back with little resistance.

And I rode it round and round the block for two miles, braking as hard
as I dared every time I went past him.

Result: A-OK. No sticking caliper. He was as confounded as I was. And
his mate said: "I've stripped loads of calipers, and I can see that
one's OK." None of us could work out what had happened. The only thing
could think of was some crap had got in the circuit somewhere and
blocked it.

Anyone got any bright ideas? It's been over two hours since he departed
on it, and he hasn't reappeared, so I guess it's OK. Bloody odd, though.

 

Ah! Light dawns. I suppose pushing back the piston was just enough to
dislodge it.

 

Well, it's an easy fix. Must have happened when I changed the fluid.

 

Thus spake The Older Gentleman () unto the assembled multitudes:

Naive question: Could this problem happen with *any* disc brakes, or is it
just something that that type of Honda caliper is prone to? I'm asking
because I had similar problems with the rear brake on my Trident during the
summer. Had the caliper/pistons looked at by a mechanic friend but he
couldn't find anything obviously wrong, and it's been fine since then
anyway.

 

I think it can happen with any m/cylinder.

The bottom of the m/cylinder on the 550 was fairly scuzzy when I changed
the brake fluid and I gave it a good clean-out with a rag. I just bet
some debris got into the hole then, or settled later.

Anyway, it was sorted.

 

It happened to my '82 BM. Bleed hole blocked with brake grease.

 

Ive had this happen twice, once was a sticking M/Cylinder piston, an odd
design which had two pistons so even though the leaver seemed to work ok the
front piston was jamming.

The second was an overfull front m/c.

I had replaced the pads but not checked how full the reservoir was, when the
callipers heated they stuck on.



-

 

Well, I haven't heard from the buyer since, and he's left +ve feedback
saying he loves the bike, so it isn't my problem if it gets stuck
again....

I tell you, it was a right bugger at the time. I was driving my son into
Croydon, and had got maybe 20 minutes away when The Doctor rang me to
say they'd brought the bike back, the caliper was stuck, and they
weren't happy.

Ho hum, U-turn, back to base, all ready to refund the £770 that was
burning a hole in my pocket, but pushing back the caliper piston sorted
it.

 

well, obviously, you just have to wheelie it more...