Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Drew400 on February 13, 2015, 02:20:01 PM
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Hi all,
I'm aware of horror stories about 400/4 brake calipers and so I'm expecting plenty of expertise on this forum (as usual)!
I haven't yet much effort into this part of the restoration. However, having refitted all the brake parts and bled the system, I'm left with a spongy lever action (that doesn't appear to do much at the disc end) and a front wheel that I can move in a rearward direction (as long as I put some effort in) but that won't budge in a forward direction.
It was all working fine when I stripped the bike down. However, since then I have replaced the hoses and unions (and of course the fluid!).
Any thoughts before I embark on a proper investigation in my garage?
Thank you,
D.
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I assume the 400 caliper is the same,or similar to the 500 caliper,
I found a strip down,and new seal fitted,remember to clean the groove works wonders,
over time the seal hardens,it is designed to flex,which is how it retracts the piston,for about £3 ,its well worth changing
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Try pumping the fluid in with a syringe from the bleed nipple, it usually does the trick
pete
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Thanks both,
I've changed the rubbers on car calipers before now, but not on a bike. Shouldn't be too difficult... famous last words?
Before then, I feel the purchase of a syringe on the horizon.
Cheers,
D.
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So you didn't take the caliper apart, Drew, remove the piston and such? That's a must on these bikes as they can get corroded.
What about the master cylinder? Does it move freely? Mine was gummed up
http://www.sohc.co.uk/index.php/topic,2367.msg22231.html
http://www.sohc.co.uk/index.php/topic,4812.msg22283.html#msg22283
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Not yet, but it's on my to do list!
Ta,
D.
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Two points to note.
1, the swinging arm that holds the back pad seizes, needs greasing periodically.
2, wind some PTFE tape around the threads of the bleed nipple so prevent it from seizing.
It looks like you need to strip the caliper though. Undo the two bolts that secure in to its bracket and pump the piston out with the brake lever. Then it's just a case of cleaning it up reassembly and bleeding it
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There are also TWO holes at the bottom of the master cyl HONEST, one big one and one real tiny one both need to be clear for it to work properly.
A good test for the master BUT BE CAREFUL is with the cap and diaphragm off you pull in the lever then let go and a jet of fluid should shoot upwards, this is after carefuly covering everything AND NOT LOOKING DOWNWARDS INTO THE RESERVOIR when doing it
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Thanks again all,
This may be a job for the weekend after next... when I've sorted out my electrical problems highlighted last week. All good fun, eh?
Cheers,
D.
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The brake arm on my original bike seized up after a winter of salted roads.
When I git this bike someone had fitted a braded hose and the arm has had a threaded hole machined in it and grease nipple fitted - apparently a popular mod for these ;D
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Thanks Clem.
Am I right in thinking that the brake arm is the bit opposite the caliper that holds the static pad (part no 45115-323-010)? If so, that part is not seized on my bike.
Cheers,
D.
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http://thumbs4.picclick.com/d/l400/pict/161558406327_/CB250-G-CB400F-Bremssattel-Halter-caliper-holder-45115-323-010.jpg
Needs to pivot freely
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I'd slap a bit of copper grease on anyway.
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The brake arm is the alloy lump that both calliper halves bolt onto
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Got ya.
Ta,
D.
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The alloy pivot pin which bolts to the fork leg has a groove or grooves that are supposed to retain some grease. The arm has to be a close fit on the pin but there are no bushings- it's not a good setup!!
You could use lithium of copper grease.... Or is there a better option?
The pin and arm being right next to the wheel and mudguard are in the perfect place to pick up water and dissolved road salt.
Has anyone tried adding o rings ?
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Correction.........New 'O' rings !
I don't remember if I fitted fresh ones or not?
The groove is actually a wide recess , looking at the parts diagram.
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I must have been lucky,mine have never seized up,
about 2 yrs ago I fitted a second disc ,so removed and cleaned the original,just packed the pivot arm with grease,just normal
med grease,made sure the top and bottom "O" rings were ok and assembled.
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Me again,
Here is the (not so) offending article. Piston looks pretty clean and smooth, apart from some baked-on fluid and the calliper body similar. Nothing that some vigorous wiping won't clean.
Looks like a new seal is all that's needed.
Cheers,
D.
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And a scrupulously clean seal groove
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And a smidgen of red rubber grease to reassemble it
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Thanks again.
I've done this work on an old car and so have some rubber grease and a little experience, unlike most of my other work on this bike (and as evidence by my posts for help).
Cheers,
D.
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All done and a rather enjoyable experience (despite Haynes saying leave to the experts).
The fiddliest part was extracting the piston. I pumped it outward before removing the caliper entirely, but it still took alot of effort to remove it entirely. Thankfully there's a threaded centre in my piston, so I could partially screw in a bolt and then clamp the bolt in the vice. Gentle prying with a couple of flat surfaces eventually enticed the blighter out. Next time I'll keep pumping until it all explodes out of the calliper!
Lots of dremmel style cleaning with a brass brush (gently) and then soft polishing heads left a relatively clean innard and o-ring recess. Washing out with brake fluid and a good blast from my mate's air compressor finished the job.
Rubber grease round the new seal and brake fluid everywhere else means it now runs smoothly and, rather importantly, it applies when I pull the brake lever and releases the disc when I release the lever.
Simple things can make one so happy!
D.
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Being happy at the slightest success must be a 400/4 owners trait Drew. I now have the horn working after a fair amount of fiddling, to most it would be a trivial mend but for me it's a major success. Just got to get all those wires, clamps and springs back in there now !!!!
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Ah, wires. I have some of those in the headlight shell I need to attend to. I'm with you in spirit!
D.