Brake Caliper Pistons not retracting

[cbigden]

Hay

I have just changed the front and back brake pads on my Honda Hornet 600.

Had to push the pistons back to get the new pads in and everything went fine. But when I pulled the front brake leaver it was very slack so I had to pump it a little, it then got stiff and the brake was applied, but the pistons are not returning causing the wheel to be lock.

Never had a problem with the old pads just had to change them for the MOT

Any advice would be great.

[Souleh]

They sound seized to me.

Pretty simple to clean down, you need to pull the pistons out of there and clean up the calipers and seals. Remove any dirt and get some nice red rubber grease in there.

Theres plenty of guides online for step by step what to do

[Souleh]

https://www.mcnninjas.co.uk/forum/index.php?topic=75767.0

[MarkJ]

You need a login for that mcnninjas link. Hornet calipers are a PITA for seizing, mine were always doing it, and yes you need to clean them - they're not retracting because there's corrosion behind the dist seals which is gripping the pistons. Get the pistons out, get the seals out and scrape the corrosion out from behind the seals (I use a very small allen key).

[cbigden]

Thanks managed to get the pistons out of the back caliper and one of the front calipers but the other side wont budge, any ideas on how to get them out?

[MarkJ]

You ideally need a brake piston tool:
https://www.cjaccessories.co.uk/images/P/piston%20removal%20tool.jpg

I don't have one, so i normally pump the pistons out till they're nearly popping out them hold them in place with a G clamp so they can't drop out and empty the system of brake fluid. I do this to all four and then I can pull them out by hand - but as you've popped one out you've lost all the brake fluid so can't do this now.

You could pull them out with pliers and something soft over the teeth, but this isn't recommended by most as it can bite into the smooth piston surface and can bend the piston out of shape - although I have used this method before.

You could also take the caliper off and blow compressed air down the banjo bolt hole to fire the pistons out.

[Rogerborg]

Mmm, if you don't have access to magic tools, I'd recommend that you put the pistons back in, refill and bleed the system, then pump them all out again evenly, as Mark said. If you don't have suitable clamps, use some pieces of soft wood to hold or push any precocious pistons back in so that they all get pushed out together.

That's what I'd recommend. What I did last time myself was to wrap a cloth around the piston, get some mole grips on it and verrry carefully tighten up until I could grip it enough to persuade it free through a combination of rotation and pulling.
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[.....]

Take the calipers to your local friendly mechanic and ask him to blow them out with his compressor.

[MarJay]

[bagger]

ive just removed the pistons out of a spare set of calipers ,i used a m16 rawl bolt just push in tighten the bolt down just enough so it grips the inside without distorting the piston then pull out
easy
(m16 is for a 25mm hole upwards)
____________________
sv650s,cb350s

[stinkwheel]

I just removed, stripped, cleaned replaced the seals and rebuilt the front caliper off my fiancees CB500s. Took me half an hour flat.

Didn't really need doing mind but it's still got this weird pulsing thing at the brakes and I'm clutching at straws.

I must say I'm impressed though. The bike has 24k miles on and the calliper is like brand new.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[pepperami]

[Souleh]

+1 warped disc if youve refurbed the brakes and still there

[MarJay]

[stinkwheel]

It's had a new disc and I had the old (actually nearly new) disc spun up on a lathe. All dial guaged up as straight. The only thing we saw was a slight up and down movement of the wear pattern on the surface of the disc.

My number 1 suspect is that the posts the disc bolts to on the wheel are distorted meaning the disc isn't in the exact centre of the wheel. The wheel itself is perfectly balanced and the runout on the rim is well within tolerances.

I'm just replacing the lot to be sure. It's getting a new (second hand) wheel, new bearings fitted, new brake line, the old disc which has been skimmed and mic'ed up as perfect, calliper overhauled and master cylinder stripped and cleaned.

I'm going to get the verniers on the old wheel once it's off and measure the hole-centres of the bisc bolts relative to the centre of the wheel to see if I was correct.

Anyway, sorry for the hijack.

With regard to the OP. I'd put the piston you have out back in. Bleed it up to pressure, put a block under the piston you've already removed with it almost all the way out then pump the other one all the way out.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[TQ]

[Souleh]

[Robby]