XJ750 front brake drags

On inspection this was noticed and the guy at the shop rebuilt the front right caliper. The bike was fine for 2 days and now it's sticking again. the guy at the shop said the other one probably needs to be rebuilt. I put the bike on the center stand and both calipers are dragging. What else could be going on? I've seen posts about a pin hole in the master cylinder floor, I don't see it in my Haynes manual though. Also, it is easy to push right forward and right reverse, as well as left forward. Left reverse is very sticky. I suppose the guy at the shop is right?

 

Hi Nick ,
I had this problem on my bike XJ750 Seca 81 and overhauled the complete system. (calipers and the mastercylinder)
I had overlooked the brake cable after overhauls, only to realise that the cable too was sticky thus the return of the brakes was not possible.
removed the cable and treated it with WD40 and got all the rust out of it.
with the age, theres bound to build up rust in between the inner cable and outer cable. Try this first , if theres no improvement ..then you have to go for a total overhaul of the system.
Once you pullout the brake mastercylinder you will come across tht TINY hole.
Good luck .

 

I had to do a couple of things on my 750 to make it quit dragging -

I used a buffing wheel to hone the pins that keep the brake shoes in the caliper down to a mirror finish, and bored the holes in the brake pads just a tiny bit with a round file, so the pads travel easier on the pins. Before that, the pads would not completely retract or retract at an angle, even with the master cylinder functioning properly.

that little return hole is a bugger too, if it's clogged up, the brakes will drag.

 

Usual/classic reason for the dragging Caliper onna Yama is that the Caliper seals need replacing.. some do this every second year.
IF they still drag after a competent reseal then the teeny hole in the master's reservoir floor may need cleaning use one of the strands of electrical wire (like found on your Bike.. for example. only) The Hole IS there beside the 2 mm one that IS visible (haynes is largely a waste of Paper IMO) Rubber hoses can become one way valves (but this is actually Rare) when the inner rubber deteriorates and swells into the tube area. Replacement..Right Now!.. is the only cure for that one.

 

I took the MC reservoir apart, I wiped the floor and poked and prodded, never found a pin hole.

I took the calipers apart. The right one looks clean and the seals look replaced. The brake pads are irregularly worn from dragging I suppose. I will replace them.

The left caliper piston had a gummy residue all around it. The seals are all chewed up. The pads on this side are worse than the other, so I'll be replacing them, too.

Don't know what to do about the pin hole.

 

You gotta find it....it's in there! And it's TINY, you can basically get one stranded of UNSTRANDED 16 gauge wire through it. TINY. Normally it sits at the bottom of what "appears" to be a spot where someone started drilling a hole with a drill, but stopped before they finished, and left a concave (depressed) area in the middle.

That's where that relief port is. If the floor of your m/c was dirty and gunky at all, you can place a sure bet that the relief port (hole) is clogged, as all that junk just settles at just such a low point......

 

I did see a small depressed area a couple of mm wide to the right of the hole descending to the brake line. I thought nothing of it because there is another one in the opposite corner on the floor of the reservoir. I was poking around with 12 gauge wire. I'll take another look tomorrow.

 

Nick....the hole is normally right in line (along the centerline of the floor of the master cylinder) with the larger "fluid transfer hole" (about 1mm diameter) where fluid from master cylinder reservoir is drawn into the m/c piston bore below the reservoir. This probably-clogged "pressure relief port" hole would be directly "behind" (on the centerline) the fluid transfer hole....."behind" meaning in the direction of the travel of the m/c piston as it is activated. When you squeeze the brake lever, you send the m/c piston heading towards the m/c brake hose fluid outlet port. The piston will "pass" the pressure relief port first, then the larger fluid tranfer hole. When the brake lever is released, the piston "returns" to it's closed position both via spring pressure acting upon it, and via fluid pressure created by the caliper pistons trying to retract into their bores, thus pushing the system fluid back up through the brake lines, against the m/c piston. This fluid needs a "pressure relief" port to compensate for changes in fluid volume as the brakes and the fluid heats up, etc.

Without this pressure being relieved, the expanded fluid has no where else to go once the m/c piston reaches the end of it's travel in its bore (brake lever fully released). So the expanded fluid pushes on the only other thing it can: the caliper pistons, keeping excess pressure on them, and thus "brake drag".

BTW: all of the above as far as the "placement" of this pressure relief hole applies to standard m/cylinders....the one on a Seca is an oddball, so I may not be describing its location and apperance correctly, but.......there has to be one there, somewhere!

 

P.S. 12 gauge wire is WAY too thick. If it is "stranded" 12-gauge wire, carefully "unwrap" just one strand of wire, and that's about the size of the pressure relief hole.....no joke!

 

I rebuilt the right brake with what appears to be success. I replaced the left caliper seals and the piston is still very difficult to slide in. There are many scratches inside the cylinder in a circle where it seems to be sticking. What to do?

 

Small brake hone, available at most automotive parts houses. Use it buy hand, not in a drill, and wet the stones with WD40. Keep it moving in and out while spinning. Follow up with 400/600/800 grit sandpaper.

ALSO, most of the standard hones come with "medium" grit stones (like 220 grit), and you have to by the finer grit stones separate in an accessory pack (finer grit is around 300). And then you have to fabricate a way to attach the fine grit stones to the same mfg. hone, since the medium grit stones "shoes" are riveted onto the hone arms! What a wonderful design. So you'll need some very small screws and nuts, also, to perform that trick.

 

Thank you so much and I'll give it a shot. I can't believe this site and how there are amazing people like you with all of these great resources. Thank you for all your help.

 

How do i use the honing tool by hand?

 

Just spin the shaft (the one that would normally be chucked into the drill collar) by hand!

 

Worked great. I bent the crap out of the antirattle spring accidentally though and I can't get it back in or even back to shape. Any suggestions?

 

I cut a piece of 0.19 ga sheet metal and made my own spring. Works great and brakes don't drag.

 

I have a similar problem with my front brake dragging. The brake works to stop the bike, but it seems like the caliper isn't opening all the way after braking.

When I open up the reservoir and activate the brake, there is a little squirt of brake fluid coming up from the pinhole, so that tells me that the hole is at least partially clear, since the brake lever does SOMETHING when squeezed. Is this how it is supposed to work? I'm going to find some wire to poke into it, but I'm just wondering what the normal action of this assembly should be.

I'd rather not disassemble the caliper assembly if at all possible, but if it comes to that. I performed my first surgery on the bike today and everything came out as intended, so I'm feeling much more confident about doing more of the maintenance on it.

 

please provide a how to with pics
my seca is dragging!

 

I am going to bleed the brakes and lube the cable before I dive into a caliper rebuild, but until then: loosening my brake cable when I park it seems to help. So does turning the handlebars back and forth all the way to each side. If it is sticking when I try to move the bike; I loosen the cable and roll the bike back and forth, and turn the handlebars. It was worse in colder weather the longer the bike sat between rides.

I haven't yet looked for the relief pinhole, but that's on the list also.

 

I got the same problem. I cleaned out my caliper a couple of years ago and it was fine until winter. I know I need to redo my caliper and master cylinder again.

Does anyone know where I can find some replacement master cylinder cover screws? Mine are chewed up.

Rusty

 

Try here...
http://xjbikes.com/Forums/viewtopic/t=2584.html
Or PM Chacal.

Or maybe someone could chime in with the diam/pitch of those screws?

Otherwise I am sure you can find something off of someone's parts bike in the forums. I posted a 'part wanted' tonight and had an offer within an hour or so.

 

Thanks for the info. I'll give it a try.

Rusty

 

Master Cylinder Reservoir Cover Screws: they're always buggered up, and there's never a better time to replace these than now! Offered in a variety of both stock (philllips-drive) and hex-drive configurations, in both plain and stainless steel.

NOTE: Original reservoir cover screws on all models were always black plated. If you wish to retain the original appearance of the screws that we offer that are zinc- or bright-plated, a quick little spray of black paint will fix that.....


The following screws fit all of these models: 1981-82 XJ550 all models, all XJ650 (except Turbo) models, 1982 XJ750 Maxims, and XJ1100 models:

HCP3040 OEM front Master Cylinder Reservoir Cover flathead SCREW, plain steel with a dark gray phsophate coated finish, phillips-drive. Each:
$ 1.50
$ 2.50 per pair


HCP5891 Replacement Master Cylinder Reservoir Cover Plate flathead SCREW, plain steel with a zinc-plated finish, phillips-drive. Each:
$ 1.00
$ 1.50 per pair


HCP5893 Replacement Master Cylinder Reservoir Cover Plate flathead SCREW, 18-8 stainless steel with a bright finish, phillips-drive. Each:
$ 1.50
$ 2.75 per pair


HCP6572 Replacement Master Cylinder Reservoir Cover Plate flathead SCREW, 18-8 stainless steel with a black-oxide coated finish, phillips-drive. Each:
$ 1.25
$ 2.25 per pair


HCP6557 Replacement Master Cylinder Reservoir Cover Plate flathead SCREW, plain steel with a black-oxide coated finish, with a 2.5mm hex-drive head. Each:
$ 1.00
$ 1.75 per pair


HCP6558 Replacement Master Cylinder Reservoir Cover Plate flathead SCREW, 18-8 stainless steel with a bright finish, with a 2.5mm hex-drive head. Each:
$ 1.00
$ 1.75 per pair



The following screws fit all of these models: 1983 XJ550 all models, all XJ650 Turbo models, XJ700 all models, 1983 XJ750 Maxim and Midnight Maxim models, and XJ900RK Seca models:

NOTE: some 1981-2 XJ550 models may also use these longer screws as specified only for the 1983 XJ550 models. You may wish to measure the overall height of your original screws before ordering. The 1981-2 screws are a total height of 10mm, while the 1983 screws are 12mm in total height. While it is acceptable to use the shorter screw in place of the longer ones, it is not possible to use the longer screws in place of the shorter ones.

HCP3041 OEM front Master Cylinder Reservoir Cover flathead SCREW, plain steel with a dark gray phsophate coated finish, phillips-drive. Each:
$ 1.25
$ 2.00 per pair


HCP6559 Replacement Master Cylinder Reservoir Cover Plate flathead SCREW, plain steel with a zinc-plated finish, phillips-drive. Each:
$ 1.00
$ 1.50 per pair


HCP6550 Replacement Master Cylinder Reservoir Cover Plate flathead SCREW, 18-8 stainless steel with a bright finish, phillips-drive. Each:
$ 1.50
$ 2.75 per pair


HCP6561 Replacement Master Cylinder Reservoir Cover Plate flathead SCREW, 18-8 stainless steel with a black-oxide coated finish, phillips-drive. Each:
$ 1.25
$ 2.25 per pair


HCP6562 Replacement Master Cylinder Reservoir Cover Plate socket head CAP SCREW, plain steel with a black-oxide coated finish, with a 2.5mm hex-drive head. Each:
$ 1.00
$ 1.75 per pair


HCP6563 Replacement Master Cylinder Reservoir Cover Plate socket head CAP SCREW, 18-8 stainless steel with a bright finish, with a 2.5mm hex-drive head. Each:
$ 1.00
$ 1.75 per pair


The following screws fit all of these models: 1981-83 XJ750 Seca models, which used one short and one VERY long screw. Original screws were unique in that they used a rather wide and LOW crown on the head; all of replacement screws have the same WIDE head feature as original, but a slightly TALLER crown on the head. Fit and function will be as original.


HCP6566 Replacement Master Cylinder Reservoir Cover Plate panhead SHORT SCREW, plain steel with a zinc-plated finish, phillips-drive. Each:
$ 1.00

HCP6564 Replacement Master Cylinder Reservoir Cover Plate panhead LONG SCREW, plain steel with a zinc-plated finish, phillips-drive. Each:
$ 2.00



HCP6568 Replacement Master Cylinder Reservoir Cover Plate panhead SHORT SCREW, 18-8 stainless steel with a bright finish, phillips-drive. Each:
$ 1.25

HCP6565 Replacement Master Cylinder Reservoir Cover Plate panhead LONG SCREW, 18-8 stainless steel with a bright finish, phillips-drive. Each:
$ 2.25



HCP6571 Replacement Master Cylinder Reservoir Cover Plate socket head SHORT SCREW, 18-8 stainless steel with a bright finish, with a 3mm hex-drive head. Each:
$ 1.25

HCP6570 Replacement Master Cylinder Reservoir Cover Plate socket head LONG SCREW, 18-8 stainless steel with a bright finish, with a 3mm hex-drive head. Each:
$ 2.95

 

There ya go Rusty... !

 

Thanks for thr responses guys. They were a lot of help.

I've been out of commission for the last week from back surgery or I would have responded sooner.

The doctor should let me ride again after my May 23rd checkup (I hope).

Until then, I'll be getting back into the forums and catching up.

Rusty

 

Unfortunately if I remember correctly from when I was getting information on my brakes last year, that squirt means you have a leaky master cylinder seal. You'll gradually lose braking ability as it gets worse. You should replace it as soon as you can.

The good news is that it's not too hard to fix, and I seem to remember there being a writeup of the process here somewhere. Rebuild kits are not very expensive, and the only special tool you need is a long-nose circlip remover (also not that expensive, and probably available from wherever you get your rebuild kit). If rebuilding the MC is all you have to do, it shouldn't take more than an hour or two for your first time (though it might not be a bad idea to rebuild the caliper too while you've got the lines apart).