Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: meerkat on September 26, 2011, 08:36:41 AM
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After 6 weeks of not using the 400/4 I went to move the bike and couldn't because the front brake is locked onto the disc.
The bike ran well the last time I used it and initially it could be moved around in the garage without a problem.
Before I start spannering today what do I need to look out for ?
All advice gratefully received.
Thanks in advance.
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The old favourite, corrosion between the alloy caliper body and the steel backing of the brake pad! Split the caliper, then apply a TINY amount of easing oil around the steel backing of the pad, leave for an hour or so, then gently squeeze the brake lever ONCE, you should see the pad start to move outwards.. apply a little more easing oil, leave for a few minutes, the attempt to push the pad back into the housing. if it moves fairly easily, squeeze the brake lever again, just once, then try to jiggle the pad out of the caliper housing. When you get the pad out, clean around the steel backing with emery paper or similar, then look at the alloy of the caliper, it will probably look white and furry. If it is, have a look at the exposed part of the piston and check for rust pits or other damage, if it looks okay, push it back into the caliper body as far as it will go. (DON'T do this if the piston shows serious rust or pitting, bite the bullet and get a replacement piston, your life depends on it!)Assuming the piston is servicable, next clean the inside rim of the caliper where the pad sits, for heavy corrosion I use a scotchbrite pad (green scratchy pad women use for washing up), followed by a polish with solvol autosol. When both the pad and caliper are clean, check the pivot of the caliper swinging arm is moving freely (If it isn't, take it apart and grease the pivot pin, A little bit of thought from Honda would have seen a grease nipple on the pivot!) Before re assmbling the caliper, apply a smear of copaslip around the edge of the pad where it contacts the inside edge of the caliper body, should help stop it happening again!(worth doing 3-4 times a year to prevent future siezures, only takes a few minutes ;D) Then re assemble the caliper, and adjust the brake to the manual spec (6 thou between the fixed pad and the disc I seem to recall) using the swinging arm adjuster bolt, then a feww pulls on the brake lever and hey presto, should be a working brake again!
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That just about sums it up!
Not sure about the women and washing up bit though. If I start to get hatemail from the libbers on the internet, I'll let you know...
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Steve, stand up for what's true, women like to wear white on the wedding day, after all, most kitchen appliances come in white!!! ;D
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They should be flattered that we give our bikes girls names. ;D
Well I do anyway.
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There are two other possibilities:-
(1) the flexis are clollapsing internaly---Would not expect that to happen just standing
(2) the tiny return hole in the master is blocked, check for this by cracking the bleed nipple open and see if the wheel frees up. This can be the cause after standing as most of us when we go to move a bike pull the lever on automatically
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The reason we give our bikes girls names is that they take all your time and money, and still give you sh*t when you really don't need it! ;D
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After 6 weeks of not using the 400/4 I went to move the bike and couldn't because the front brake is locked onto the disc.
The bike ran well the last time I used it and initially it could be moved around in the garage without a problem.
Before I start spannering today what do I need to look out for ?
All advice gratefully received.
Thanks in advance.
Thanks for your replies and advice.
I had a look at the bike this morning after a camping weekend away and applied a couple of drops of PlusGas to the top of the caliper pivot, prior to a strip down.
Success !
The brake eased off and I was able to give it a good run of 46 miles without any problems.
Let's hope this good weather lasts a bit longer !
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In that case you need to remove the pivot and clean thouroughly re assembling with copaslip
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In that case you need to remove the pivot and clean thouroughly re assembling with copaslip
Thanks Bryanj, the job's scheduled for the next spell of wet weather. :)
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As a Mech Fitter we're told never to use copaslip on ali coz of corrosion, on casing screws we get away with it coz the screw head tightened into the casing stops moisture getting in, but on the caliper pivot it can and in ali is 'sposed to react causing electrolitical corrosion.
I used normal grease and renewed the O'rings on the pivot.
I 'spose the O'rings should stop the moisture getting in ::) :D
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I've used for years a marine type grease that's used in outboard motor mount pivots and launch trailer wheel bearings amongst other things, seems to resist seizing quite succesfully and there is no real heat requirement there. Just seemed to match the application when I originally bought it.
I'll look at what I've used and post it (can't remember the name offhand).
Never owned a boat though!
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Yep I have a tub of waterproof grease, normally use it on my trailer wheel bearings coz it lives outside and doesn't have body work like a car to stop the rain getting in.
I use this Clicky (http://www.foxsonline.com/acatalog/Morris-K-99-Waterproof-Grease-AF2-74911.html)
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After 6 weeks of not using the 400/4 I went to move the bike and couldn't because the front brake is locked onto the disc.
The bike ran well the last time I used it and initially it could be moved around in the garage without a problem.
Before I start spannering today what do I need to look out for ?
All advice gratefully received.
Thanks in advance.
Finally after deliberating whether to strip the front brake system down or not, I bit the bullet today.
Penetrating oil on the pivot had made things slightly easier but the brake soon jammed on solid again.
The caliper piston was seized in the caliper and took ages to remove.
Result - ancient brake fluid, loads of rubbish in the caliper together with a seriously rusted piston.
Now to source a rebuild kit and fresh brake fliud.
Thanks for all the helpful replies so far.
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That's a brilliant example of what happens to these brake pistons...
Ouch!
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Dave Silver is now doing stainless piston cheaper than genuine(
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Dave Silver is now doing stainless piston cheaper than genuine(
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Let us know how you get on with Kevin's piston.
I've heard a lot about them.
S
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Don't forget to clen out the seal groove really well or the piston will still be tight
While refurbing the the brake systems (and more) of other motorcycles, I made pretty good experience with car type rim-cleaner (Sonax, etc...), which removed/softened all kinds of deposits very well.
Also used it on aluminum engine/gear casings without any noticeable corrosion.
However please proceed with care, as I yet don't know personally about the effects on the materials used on those older bikes!!
Use as advised, apply, let soak for 2 minutes at max (might use nylon brushes there), rinse carefully with lots of water; repeat procedure if necessary.
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I've fitted one of those phenolic pistons about 5 months ago and everything seems fine.
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Let us know how you get on with Kevin's piston.
I've heard a lot about them.
S
First off, the service from Kevin was excellent ! ;D The piston was with me in good time and I fitted it today for a quick road test.
After stripping the caliper down, I found the source of the problem which was the badly corroded piston.
While the caliper was stripped, I drilled (5.5mm drill) and tapped the caliper arm for a 1/4" x 28NF grease nipple and cleaned the pivot bolt up. New brake fluid to replace the emulsified muck that was in there and the bike was as different as chalk and cheese.
Many thanks again to everyone on here for the good advice given.
Photos added.
Postscript. Just had a run out to renew the MOT. Passed OK. ;D