Honda-SOHC

SOHC.co.uk Forums => CB750 => Topic started by: Coppertop1234 on May 24, 2015, 07:08:09 AM

Title: Front Brake Callipers
Post by: Coppertop1234 on May 24, 2015, 07:08:09 AM

Front new master seals fitted with new braided hoses and pads
No joy the piston is seized all the way home in the recess

Tried to move it with an air line stuck solid
Present line of thought is to soak in rust release and try airline again
Failing that I would presume attacking the piston to remove and replace

Are the 400/4 front callipers the same size?

Not tried back ones yet,but expecting the same

Any tips appreciated

Cheers

Keith Snr

Title: Re: Front Brake Callipers
Post by: royhall on May 24, 2015, 07:45:57 AM

Best thing to do. If you have a master cylinder, connect it to the caliper with one of your hoses. put some brake fluid in, a quick bleed, then pump the piston out with the hydraulics (you will need a handlebar or a length of tubing to enable you to squeeze the lever). Be ready with a rag to catch the fluid when the piston pops out. Works nearly every time, you wont get it out any other way without damage. O and keep you fingers out the way as it sometimes goes with a bang.

Title: Re: Front Brake Callipers
Post by: Bryanj on May 24, 2015, 11:31:16 AM

If you remove the nozzle from a grease gun the hose will thread into the pipe fitting on the caliper a couple of threads DO NOT FORCE IT AS THEY ARE DIFFERENT then with bleed nipple in pump grease gun to force piston out----never failed yet

Title: Re: Front Brake Callipers
Post by: hairygit on May 24, 2015, 12:03:04 PM

No, they are NOT the same as 400/4, 500/4 and 550/4. The calipers pn the F1 were also fitted to the K7 ans u,s, market automatics, so good used ones are rare and expensive, thankfully Dave Silver does an exact replica now, so all is not lost if you do damage it.

Title: Re: Front Brake Callipers
Post by: Spitfire on May 24, 2015, 12:56:17 PM

The F1 front caliper used to be like rocking horse poo to find but as has been said David Silver spares now sells a replica, here is a link to a chart that I made out a while ago on interchangeability
http://www.sohc.co.uk/index.php/topic,1562.msg1650.html#msg1650

Cheers

Dennis

Title: Re: Front Brake Callipers
Post by: Coppertop1234 on May 24, 2015, 02:51:20 PM

Thanks for info all
Soaked the calliper in rust remover (B&Q) over night
Washed it clean and flushed with brake fluid several times
Eventually the piston started to move - Result
I think the key was the overnight soak, as the piston rust was minimal - not pitted or damaged in any way
Removed piston cleaned the surface with metal polish - (Autosol)
Seals were fine for now but will replace at later stage

Front calliper working fine ;D

The joy of the back calliper is still to come

Cheers

Keith Snr