Dirty Pictures inside......of my brake caliper

[Pigeon]

My bike had a service a while ago, and afterwards the front brake was amazing (all relative). But on closer inspection, it feels like the pads are binding to the disc. Takes a bit of effort to rotate the wheel by hand, friction noise present.

It's a small Chinese 125 ( Jianshe JS-1256a ). Marketed as an AJS JS125-E2
Part of the point of owning this bike is I'd like to service it myself.
Problem is, there is no service manual for it. And the generic Haynes Chinese Bikes manual does not cover this specific model, but I'm using that and Youtube clips trying to get a handle on things.
Done an oil change and tightened the chain.

Single pot caliper.

I've tried using the bb code img quotes and can't get pics to embed, so links are below instead:

pic1
Black hose into gold union bolt?
To the right is the bleed valve, again gold, small black cap?
To the right of that, the medium sized black disc. Appears to be a rubber cover maybe. To the right of that is one of the silver bolts that holds the caliper to fork.
Below the larger disc shape (piston?) is a small rubber thing. I gave it a pull and it stretched 5mm out. I gave it a push and it squished in. Is this some sort of finger pump thing? You can better see it in pic2, with the number 39 on it.
another pic at slight angle

pic2
Pic2 is just a shot of the underside.

It was my understanding that to clean a caliper
1. Slacken the caliper bolt (not those which attach it to the fork, but those that go through the caliper itself. But where on mine is that/those?
2. Remove two bolts holding caliper to fork
3. Remove shim/clip and let pads fall out together to avoid grit / oil getting on them.
5. Use soapy water and toothbrush to clean around piston, taking care to not damage seal.
6. Check wear markers on pads.
6. Push piston in, press break leaver to check piston comes out smoothly.
7. Re-assemble.

I'm guessing that the bolt I first need to slacken might be hidden behind a possible rubber/plastic cover in pic1. That medium sized circle to the left of the first fork bolt.

But, I don't want to do what I just did, and push / pull, stick a screwdriver in and end up damaging something. Like I might nearly have done just tugging on that small rubber thing at the base.

I'm grateful for any pointers / explanations of the pics and what I should do. I'm keen, but usually cock it up

Many thanks!

[Polarbear]

Single piston sliding calipers. The bit that squished is the caliper slides that allow the caliper to centralise when the piston moves.

https://img33.imageshack.us/img33/9207/index1uj.jpg

You can the the caliper slides in the image below.

https://img836.imageshack.us/img836/8104/l20025tdnewfrontbrakeca.jpg
____________________
Triumph Trophy Launch Edition

[el_oso]

undo the bolts that attach the calliper to the fork. The calliper will then wiggle around. Keep wiggling it to slide it off the disk.
once free take out the pads and retaining clips etc.
you now have two options
-pop the pistons out by pumping the brake lever
-move out the pistons with the brake lever, but go slowly so they don't pop out (just before winter, this would be my choice as long as they aren't terrible)

assuming you have gone with choice number two, spray some brake cleaner on the pistons and rub away the crud and crap with a brush. brake cleaner evaporates quickly and doesn't leave a residue that will contaminate your brakes; plus it's bloody good at removing dirt.

see the thread on brake cleaning, or search youtube for sliding calliper removal and clean. Yours look like sliding callipers and they all operate more or less the same way
____________________
Duke 390
Previous: '05 XR125L | '96 XJ600S Diversion |'05 Suzuki GSXR1000 | '05 Honda CBR125-R | '97 YZF 600R Thundercat | '11 Honda CBR250
Car: Jeep Wrangler 4.0L

[Pigeon]

Many thanks guys, this info is exactly why I asked. I would have tried to shove a screwdriver in that medium sized cap at the top expected to expose a bolt and probably done more harm.

A job for Sunday. Question is, will I be taking the bus on Monday

Many thanks.

[janner_10]

As you own a Chinese bike I would get a bus pass!!

In all seriousness, if you keep up with the maintenance, you should be ok.


Sort of
____________________
Yamaha FZS600 (Now gone to heaven) > CBR600F4i (SOLD) > '99 YZF-R1

[Pigeon]

I've had the bike 18mths + 8,000miles, its been parked outside 24/7/365, it's been ridden daily regardless of weather (except for 2 weeks when the snow was too bad).
It's been great, started every time, never cut out, never left me stuck. Averaged 112MPG
OK it's slow, suspension is basic (I'm 16st) and washing it twice a month is a must. But it always puts a smile on my face and I want to try my best to keep it that way.

So I undid the two bolts holding the caliper to the fork then I undid the two bolts that ran through the black casing and brake pads . There was some crud in here, but I used a toothbrush with warm soapy water, then a houseplant sprayer with plain warm water to clear it out. The bolts that ran through the casing and pads are poor quality. They had some scoring and crud on the smooth part of the bolt. So I used some fine emery and smoothed them, then added a very thin layer of grease to the smooth part of the bolt.
There was some small build up on the 1st 2mm of the piston, but I pumped the lever to get 15mm showing and cleaned it up

I tried to take a video of the piston moving when repeatedly pulling the hand lever. Piston seemed to be ok, video a bit shakey .

What I don't understand, there doesn't appear to be anything that forces the piston away from the pads. Squeeze the bar in and the piston moves out 1mm, let the bar back and the piston moves back 0.25mm ish. Is this how these basic ones work?
The net result is the pads are always, to some degree, in contact with the disc. There is noticeable resistance when rotating the wheel.

Is it just a crappy caliper. Or should I have gone further and taken more of it apart somehow?
Having had the part off, I'm still clueless as to what I could have taken apart to check out.

I put it back together, used some 99% isopropyl alcohol to clean the disc.

Looks like I'll be riding to work behind the Bus on Monday

I'd like to have a go at putting thicker fork oil in at some point, check the timing, replace the chain+sprocket, clutch plates, tyres etc
But if it aint broke...... and before you say it, "being Chinese it won't be long before it does break"

[mentalboy]

Sounds like the piston is binding. You've got one of two options if it is.

1 - remove piston and clean pot and seals, this may reveal more nastiness than you want to get involved with ( and a new set of seals if you're not careful!)
2 - Use small cramp and retract piston, hold piston in place with cramp and bleed through brakes to remove any crud, then release cramp and pump out piston ( probably be best to put a lump of wood in caliper mouth to prevent piston flying out of cylinder, lucky this didn't happen in vid!)
Then retract piston, pump it out, retract, pump out and do this until piston moves out freely, if you're lucky it'll work or you'll have to go to option 1.
____________________
Make mine a Corona.

[kramdra]

I have a similar issue with my brothers chinese 125. The brake system was new to replace the old one. Good bikes apart from that.

Test if the binding stops after bleeding out some fluid. Careful not to let air in. This is the temporary fix I use. It lasts a couple of weeks/month. Keep an 8mm? spanner and some tissues with you incase

for the amount of movment in your video, I think calipers probably fine.

Check your brake lever is not pushing on master cylinder piston, as it wont let fluid return if it is. THIS has caused a few crashes with chinese levers on sportsbikes. But I dont blame the levers, it should be checked and adjusted on installation.

I may have damaged the piston/seals pushing pistons back in when taking the wheel out once.

HOWEVER for a new system, the fluid is a really shit brown colour, when new fluid should be clear. So Im blaming fluid/possible master cylinder blockage. Have intended to change fluid for a while now.. might do tomorrow.


Would like to try/see some radial tires in it, but cost too much.

[Pigeon]

[YBR Ric]

On your bike there wont find anything to adjust, but you can easily check for interference damage by removing the brake lever and see if anything changes as any possible pressure on the master cylinder piston will have been eradicated.

Basic caliper designs of this type will rub to some extent. It's only when you run a fixed caliper multi piston design that things change.

[Pigeon]

Thanks Ric. I know last winter the disc was rubbing on the pads as it was audible and the disc very hot with little use. As with most parts on the bike, it does the job, but is cheap and clearly has limits.

I will remove the lever tomorrow. Have also bought some DOT4 and will have a crack at replacing whats in there (been 18mths).

Spent a couple of hours today installing a 250w Metal Halide Floodlight inside the garage. No more groping around under poor light. Might even get a tan