FRONT BRAKE

Hi folks

I had a 16k service on my CB500 by local mechanic. When dropping it off I asked him to have a good look at the front brake as the slightest pressure on the lever had the brakes applying quite sharply. He said he had stripped it down, everything seemed fine apart from a little corrosion on one of the pistons. He cleaned it, rebuilt it and all was how i expected it to be. He said that the piston would need replacing eventually but not yet. That was 4 months ago and now the same 'slightlest touch on lever = sharp brake' feel has come back.

By big question is, how easy is it to replace front brake pistons. I presume best to replace both pistons? Best to change seals as well?

Any advice appreciated. I have the Haynes but thought I would ask those who have probably done the job themselves before.

Ta very much

Simon





*****JUST TO ADD - I AM HAPPY TO STRIP DOWN THE CALIPER AND CLEAN THE POLISH THE PISTON UP AGAIN RATHER THAN BUY NEW. COULD UPLOAD A PHOTO OF IT TO GAUGE OPINION AS TO WHETHER OR NOT IT ACTUALLY NEEDS REPLACING.

Change the seals, don't even consider skipping that. Don't change a piston that isn't damaged, but even minor damage/scoring to a piston is a cause to replace it. If you can clean them up spotless, great. If you can't, you need a new piston (Note: If the piston is only damaged in a part that will never pass over the seals, it doesn't need replacing - but think it through carefully as the position of the piston will change throughout the life of the brake pads). I wouldn't bother replacing both pistons if only one was damaged.

Things that can go wrong include getting the piston stuck if you let it try to come out at an angle, and the bleed nipple snapping off due to having seized in place (prevention methods include lots of PlusGas, the superior cousin to WD40, and 'shocking' it off by twisting suddenly rather than the gradual and progressive pressure that can cause it to break). And recommend against using a metal anything to remove the piston seals - find something plastic instead (e.g. plastic-bladed screwdriver).

As you can guess, i've learned some of these things the hard way

Hi

Thanks for your reply

The pistons on my cb500, why are they a black/grey colour? I have a cb1300 and the other halfs bandit in the garage - both bikes pistons are a shiney gold colour. The pistons on the 500 dont appear to be made of the same material.

Any ideas?

Thanks

Also, apart from the trusty old haynes, anyone got any how-to's for stripping calipers and replacing pistons and seals.

I have never displaced a caliper before, but happy to try and give it a go.



thanks

cb1300rider wrote:The pistons on my cb500, why are they a black/grey colour?

It's just the colour they are to be honest, nothing to worry about

cb1300rider wrote:Also, apart from the trusty old haynes, anyone got any how-to's for stripping calipers and replacing pistons and seals.

I don't know of any how-to's, but when I've done them in the past I pump the pistons out as far as they will go with the brake lever, keeping them level with an old pad pressed on the faces. Quite often you can get them both to pop out with this method but if the seals are really shot you'll make your life a lot easier with brake piston pliers.

If it makes you feel any better, I recently had to service the front master cylinder after the brake stopped working.

Got hold of the service kit ok (David Silver spares is only up the road, and they were very helpful in working out the right bits etc)... on stripping the master cylinder I found what appeared to be a large seal ahead of the piston - this item being missing from the overhaul kit.

On closer inspection, the extra 'seal' turned out to be..
a PIECE OF PAPER!!!

The piston was pushing this up against the outlet to the brake line.
I have no idea what someone was thinking when they put it in (I don't think it was accidental..). Sure scared the lights out of me

Good luck,
Vexx

Hi,

have a look at the pad pin, they often get grooved and the pads can't move smoothly.

Bit of a mystery why brake comes on with slight pressure. Perhaps try riding in summer gloves to see if you get more feel. Also, if you're worried just buy another caliper from ebay to check yours against.

m1

Vexx wrote:..........On closer inspection, the extra 'seal' turned out to be..
a PIECE OF PAPER!!!

.....
Vexx

Far canal!!

more sewer than canal...

Vexx