Pistons pushed too far back

Started reassembly of front wheel on ER5 but think I've pushed caliper pistons back too far

Basically caliper will not bleed and have fluid leaking from seal, pistons won't move forward at all, tried putting air compressor onto caliper to push them out and they won't budge.

Any ideas how to get them out? Or have I f**ked caliper?

The pistons should fit no matter how far you push them in, the sides are straight.

What have you done? Is this a full caliper refurb? Have you used proper Kawasaki seals or knock offs?

Nothing with the seals, they were fine so didn't touch them caliper taken off, wound pistons back and cleaned caliper down. Then been sat for couple of weeks till today when I put front wheel and forks back on.

Did you use a lot of force to push the pistons back in? Was there a lot of corrosion/dirt on the pistons?

My guess is you've knackered a fluid seal, though maybe it's just not sealing well on an uneven surface. You can get tools to get the pistons back out or, if you're an animal, you can chew them up good and proper with pump pliars (please don't do this). If the pistons are so hard to move I would imagine the seal grooves need cleaning out, corrosion builds/grows behind the seals and pushes them on to the piston, making it not want to move. If the pistons were as free as they should be then you could push them in by hand. Sadly that is almost never the case as bike brakes are made really very badly..

They did take quite a bit of force to push back tbh didn't think anything of it are the time as used to car ones being a PITA to push back at times (bent the metal rod on wind back tool doing current car ones, they are horrendous).

Did not see any noticeable dirt or corrosion though.

Well will give compressor another try if not will have to get a set of those removers.

Grease gun on bleed nipple.

sounds like the seals are shagged to me!

without them sealing right you may have a job getting them out! or as megawatt says try a grease gun! grease is a bit thicker than brake fluid so you may get some movement!

PS you can't push pistons too far back

If they were hard to push back in, maybe you didn’t open the reservoir?

Firstly, did you prize out the seals and remove all the mineralization and crap from the grooves that the seals sit in ? If not then this is what might be making the pistons hard to push back in . If it were me I wouldn't mess around with grease guns or compressed air, I would just reassemble the system, bleed the air and then pump the pistons out with the brake lever. If the caliper is useless then you have a good excuse to do an ER6 upgrade as suggested in one of the Pony Power youtube videos. Good luck.

If they were hard to push back in, maybe you didn’t open the reservoir?

The reservoir has an expansion bellows and a vent but removing the cap might have helped. I could push mine in easily with my thumbs so something isn't right.

Broom handle or such like ... wrap shed loads of gaffa tape around it .. make it so it is oversize to the recess in piston ..force it into said recess and twist as you gently pull outwards

[mention]Westbeef[/mention] When pushed back in caliper was completely detached from bike including brake line and no way they could have been pushed in by hand, used a small g clamp which pushed them back fine but was hard work.

[mention]fastbob[/mention] They haven't been disassembled at all, apart from looking a bit grubby and low pads caliper looked fine so left it as is just pistons pushed back and cleaned, won't come out at all with brake lever. Tried yesterday and just leaks out of seal and pistons in same place despite multiple pumping of brake. Got the 2001 model with the ER6 caliper already

Seals were definitely ok before so thinking when pushed back I've pushed the end bit of piston (the normally uncovered part that picks up all the crap) past seal so won't seal now.

Will drag myself out of bed in a minute to try getting them out without destroying and update.

Did you put some Red Rubber grease on the pistons before pushing them back in?......If not, the piston has probably pulled the seal and wedged it......

When I'm maintaining my brakes on the bike I keep cleaning the pistons and applying a small amount of red rubber grease until I can push the pistons back in by hand.....and that's with the caliper all connected up.....

Update... Ignore everything I've said so far lol

Seal not leaking as running down from a loose banjo... Caliper is fine BUT my master cylinder is knackered, taken of bike and filled up nothing pumps out of it... When bleeding it did get jammed in so took it off and managed to get cylinder unstuck (hence loose banjo ) but guessing internals still jammed as it does naff all.

Got a spare one to use for now but not really in with appearance of rest of bike lol...

But ... if you have tried using air compresser to force the pistons out without success then there is still an issue with calipers .

They are still very tight but new cylinder moved them with ease (and they do move back enough to not lock when pressure released).

That said I think a rebuild definitely needed so all coming off again till that's done.

They are still very tight but new cylinder moved them with ease (and they do move back enough to not lock when pressure released).

That said I think a rebuild definitely needed so all coming off again till that's done.

False alarm then . If you didn't take the seals out and carefully scrape out all the mineralization from the grooves they sit in then you definitely need to do it next time . To get the pistons out you need to pump them out as far as possible but they need to come out equally. So if one takes the line of least resistance, it needs holding back until the other one catches up. As its a one sided floating caliper why not just remove the pads, put it back on the bike and pump away ? Provided the combined thickness of the pads is just less than the depth of the pistons, this should bring them far enough out to enable them to be pulled out easily. You could try it with one pad first to see how its going . A gentle pulling and turning motion with Mole grips and a piece of rubber inner tube to protect the outer face worked well for me when I did my GSXR and that's 12 pistons ! Also very important on this particular caliper is to make sure it floats freely on its pins so they need cleaning and greasing . Finally if you're needing a g-clamp to get the pistons back in there's something wrong . Two strong thumbs should be enough.

That's a lovely looking master cylinder but where's the mirror going to go ? On mine I just sanded all the raised lettering off the cap and polished it. I also installed a master cylinder repair kit. In case you are wondering, my cover got shredded in the storm last week, the ER has to live outside because I only have indoor space for one bike . Not exactly riding weather today http://i.imgur.com/nYFM4SL.jpg

Same weather I've got so given up for today, not much more I can do now anyway.

Got the pistons out, even at the end they were a nightmare used a spanner to stop one popping out before the other, with about 5mm worth of piston left one pulled out on the other still stayed stuck, got it it in the end but was stupidly tight.

Will get some new seals now, not sure if I should just bite bullet and order new pistons or attempt to clean them up myself.

The new lever has got mirror hole but after all the effort to dechrome rest of bike it looks odd now lol, so new master cylinder to order as well. So much for no more expenditure lol.

Pistons cleaned up ok, put some tape round a torx socket piece then tapped into piston and put into bench drill and cleaned with abrasive pads got rid of all corrosion but little pitting nothing to be overly concerned about though.

Pistons cleaned up ok, put some tape round a torx socket piece then tapped into piston and put into bench drill and cleaned with abrasive pads got rid of all corrosion but little pitting nothing to be overly concerned about though.

So is there a load of crap ( mineralization ) in those grooves ?

Not really but the seals seem very 'sticky' even cleaned down they don't want to slide over seal, didn't want to try too hard as would need them out again for when I get new seals.

Got a seal kit for £20 and 2nd hand master cylinder for £16 so not too bad.

Don't forget the Red Rubber grease.....

Don't forget the Red Rubber grease.....

All refurbed and second hand master cylinder turned up today so all ready to go back on bike.

Can see one cylinder is a bit more pitted but feels smooth and no leaks.