Front brake caliper pistons stuck

[oldgreyandslow]

I've searched some previous threads on this and have tried most of the suggestions, my problem is trying to retract the pistons just using the master cylinder, the larger ones move but the smaller ones seem stuck solid. I've tried tie wraps on the larger ones etc but still no movement.

Anyhow on another thread someone posted a link to a piston removal tool that looked a bit like a fancy pair of pliers, which I can't now find.

Any ideas or suggestions on a suitable tool or removal method?

Thanks

[scotjell]

Might be a silly question but are you trying to push them in or get them out? The reason I ask is you say you're using the master cylinder?? If you want to retract you should have the cap of the reservoir to allow the air/oil out to enable them to retract. If you want them out you'll need to put something solid between them minus the pads and pump maybe wise to soak them in brake cleaner or sometimes people use diesel. You can air blast them out but this will get the easy ones out first then you struggle! I usually put something about flat file width between the opposite pistons and pump make sure you have it on both sides though or whilst your watching one caliper the other sides pistons will pop out.

[oldgreyandslow]

Should have said I'm trying to get them out not back in

[arsey30]

Is the reservoir empty, if you pushed some pistons well out, you may be drawing air.

[RoninZX-10R]

Youre going to want to get yourself a pair of Draper motorcycle brake piston removal pliers. I bought a set off eBay for about 16 quid. Worked a treat.

[gpz900]

If you've already popped the big pistons out and therefore lost your hydraulic pressure, it's a bit of a pain, but it's probably worth putting them back in and bleeding them. I've had to do this before.

Work on one caliper at a time, put something solid between the pistons on the other caliper so they cant move.
Put something solid between the big pistons on the caliper you are working on so they can't move either.
Squeeze the lever, if the system has no air in it and only the small pistons on the caliper in question are able to move, I'd be amazed if they don't.

Keep going until they are almost out but not completely, then put something between them so they can't move further. Then move onto the other caliper and repeat.

Once all the pistons are almost out, you can drain the system and split the calipers.

I usually use mole-grips with something covering the jaws so I don't scratch the pistons, be very careful as they are quite soft. You can also use compressed air to pop them out but be careful, when they come out they come out hard.

Clean the crap of the pistons with fine wet/dry and or fine steel wool.

Take out the old seals, (there's two per piston) and throw them away cause you've got new ones, right?

Clean the calipers with brake cleaner making sure you carefully scrape any crap out of the seal recesses.

Clean the calipers thoroughly with brake cleaner.

Smear the new seals with rubber grease and fit them.

Lube the pistons with clean brake fluid and pop them back in.

Put the calipers back together and bleed.

Good luck. :)

Al.

[oldgreyandslow]

Thanks folks

Is the reservoir empty, if you pushed some pistons well out, you may be drawing air.

I'm pretty sure its not drawn in air

Youre going to want to get yourself a pair of Draper motorcycle brake piston removal pliers. I bought a set off eBay for about 16 quid. Worked a treat.

Thats the one

And to save a huge quote/reply: gpz900/Al
Thanks for the detailed reply, pistons are all still in, the large ones were nearly out though, new seals on order, red rubber grease already got. I'm going to split, clean, paint calpiers and fit HEL lines

Its just finding the time in between working for a living!

[arsey30]

Your hydraulic brake system will excert far more pressure on the pistons that you can by hand with pliers.
Did you top up the reservoir whilst pushing out the pistons, if 2 are nearly out, fluid will be low.

Do the large ones still move if you remove the tie wraps?

[oldgreyandslow]

Your hydraulic brake system will excert far more pressure on the pistons that you can by hand with pliers.
Did you top up the reservoir whilst pushing out the pistons, if 2 are nearly out, fluid will be low.

Do the large ones still move if you remove the tie wraps?

Dave,
I was hoping to use the pliers once I'd got the pistons pretty much out. I didn't top up the reservoir, best check that. Yes the large ones still move, I've tried pushing and tieing them well back, will try again later.

[oldgreyandslow]

Update:

One piston appears to be a bit scored, anyhow they are now all out as far as they can go, pretty much butted against each other.

So I guess its time to crack the caliper bolts and disconnect the hoses and separate the calipers. Once separated how difficult is it to get the pistons out? My last bike didn't have calipers you could split and I recall that being a bit of a pain.