Brake Caliper Siezed?

[Drew400]

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.

[Johnwebley]

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

[UK Pete]

Try pumping the fluid in with a syringe from the bleed nipple, it usually does the trick
pete

[Drew400]

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.

[tom400f]

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

[Drew400]

Not yet, but it's on my to do list!

Ta,

D.

[mike the bike]

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

[Bryanj]

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

[Drew400]

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.

[Clem2112]

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 

[Drew400]

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.

[tom400f]

http://thumbs4.picclick.com/d/l400/pict/161558406327_/CB250-G-CB400F-Bremssattel-Halter-caliper-holder-45115-323-010.jpg

Needs to pivot freely

[mike the bike]

I'd slap a bit of copper grease on anyway.

[Bryanj]

The brake arm is the alloy lump that both calliper halves bolt onto

[Drew400]

Got ya.

Ta,

D.