I broke something else: this time my Tiger callipers

[Fallout]

So did a routine inspection of my pads on the Tiger 1050 and noticed both callipers had more wear on one side than the other. Since it's a 2006 and probably never had the callipers rebuilt, and I've successfully done this with the Gixxer, I thought why the fecky McFeckerson not?

Whipped them off, whipped them apart, whipped them just for the sexual thrill of whipping, and then whipped them inside for a rebuild. Because a new seal kit for 2 callipers is £60 and is essentially just a few rings of rubber/plastic (ie. you're purchasing a rogerring), I decided to reuse the old seals. Upon inspection they were completely blemish free and still a snug fit, so why the hell not? Pistons were in good nick, with tiny little bits of corrosion at the furthest surface but otherwise ok.

Cleaned everything up like a hitman with a box of Daz, left it all to dry overnight and then set about rebuilding. Red rubber grease used sparingly for all seals which slotted back in nicely, brake fluid to ease the pistons back in, which seemed to go in nicely after some wiggleage. Happy so far!

Old pads back in, callipers reinstalled, all hooked up, cheatingly bled with a Mityvac, lever firmer than a an athlete's glutes. Splendid! Wheeling the bike about it did seem like the pads were gripping the surface of the disc a bit much though. Hmmmm, I thought. Hmmmm!

Today I decided to rebed in my pads, but sensibly stopped just round the block to check the disc temps. Right warm acceptably warm, left one was light fondling napalm so headed home.

Hitched the front wheel up, and with a good spin it will do 3/4 to 1 revolution at the most.

I can push all the pistons back in manually with a flat head screwdriver, so they're not jammed. I don't know how difficult this should be, but it was fairly difficult. I will remind you after getting the piston past the inner seal they slid in easy peasy.

Refitted callipers and left the pads well clear of the wheel. Rebled in this position, in case somehow I'd introduced too much pressure or something using the naughtyVac. I then brought them in using the lever alone and they gripped well. Good lever! But again, wheel cannot be spun and they're not returning well.

So what are the possible causes? My thoughts ...
- Master cylinder isn't sucking, but this sounds silly. I would've expected a spongy lever if the MC was broken in someway?
- Pistons simply aren't sliding back because the seals are fecked for some reason, even though they can be pushed in with a screwdriver, and went in pretty easily after the rebuild
- Something else!

Obviously this is a particularly annoying problem because apart from reusing what looked like preferly good seals (which weren't leaking before or anything), I did everything by the book and have only made things worse! BOOOOOO! BLOODY BOOO!!!

[Sid Squid]

Some possible causes:
Piston/s not moving smoothly.
Pads sticking in caliper.
Master cylinder relief port blocked/obstructed.
Cheap- ass poor fitting brake lever not allowing master cylinder to retract properly.

[Bibio]

are the callipers the 'sliding' or 'opposed' type?

I vote for the plugged master cylinder relief port.
Enjoyed reading your post Fallout.

[Fallout]

Hah, thanks Wideguy.

They're radial opposed callipers. The brake lever is factory, so hopefully decent enough, as is the MC. While MC may seem the culprit, it was fine before I destroyed everything. Some others have suggested it's the seals. I've head several people say it's the seals that squidge up and are responsible for returning the piston, and with hindsight I know some seals are directional, so it's possible these are too and I've put them in the wrong way.

I'm just hoping it's not the MC. If I just need to buy some more DOT4 and fiddle with the callipers and seals for a bit, I'll be happy. If that doesn't work, perhaps I broke the MC with some vigorous squeezing while bleeding? I have been practising my vigorous squeezing lately and become quite good at it.

You won't break the M/C by squeezing on the lever! I've tried.

You opened the system, including at least the reservoir cover. That means there's a chance you either introduced foreign material into the system, or just stirred up some that was there waiting, which means something could have gotten into the relief port.
When you have the front end on a stand and apply and release the brakes, the front wheel should spin fairly freely. Not like it would if you had the calipers off, but it should spin easily. If the pressurized fluid can't escape back into the M/C, it will make your brakes drag. Both sides. Plugging the relief port will keep pressure in the system and cause this problem.

[Fallout]

Thanks mate. Ok, well I guess the solution is to take it apart then and see if I disturbed something in the MC. I was careful to keep it all clean, but as you said, I could've disturbed something in there already. I'll stick with the dodgy seals theory for now, as that's known territory and the bit I've fiddled with, and if I don't have success there I'll go for the MC next.

[Bibio]

looks like you may have twisted a seal.

if the radial MC is like mine there is a plunger pin than can become unlodged at the lever end, its a barrel with a recess which the pin sits inside and sometimes the barrel at the lever turns which causes the MC plunger to be always on, common fault when people fit aftermarket levers or doing maintenance on the braking system.

[Fallout]

I didn't do any tomfoolery at the lever end, apart from opening the reservoir and lever squeezage, but I will definitely double check that. Cheers bibs. I'm going to make this a priority tomorrow so will open up the callipers and see what mess I've made then report back.

[Fallout]

Ok, so turns out the main fluid seals are directional. The correct direction is apparently thick end towards the disc, according to Haynes and the one forum post I could find about it online. Rebuild the callipers without red rubber grease. Then hooked them up and started pumping them out and pushing the pistons back in, over and over until they were all going back in and coming out smoothly, nicely lubed with brake fluid. Put the callipers back on and everything seems to work now. Wheel can complete maybe 1.5 - 2 revolutions with a good spin, which feels right compared to the other bikes I've had .... so I think I fixed it.

Lesson learnt ... seals are directional! On the plus side, a lot learnt about rebuilding callipers.