Help needed: Brake Pad troubles 750 Maxim

Just put new front brake pads on my 1983 XJ750 Maxim, but now I can’t get the rotors to fit back into the callipers. The space between the pads isn’t enough for the rotors to fit. Fairly new to the DIY scene so I’m hoping to avoid a calliper rebuild but it’s not out of the question.

Any suggestions would be much appreciated.

 

Pull the pads back out.

Use a c-clamp to push the caliper piston back into the bore (take the cover off of the master cylinder and watch it as you work so you can remove excess fluid as the piston goes in, otherwise you'll have a huge mess to clean up).

Reinstall the pads and you'll be able to put the calipers back on.


Now for the big and really important question.

What are the date codes on the brake lines?
Rubber lines are considerd a wear item and should be replaced if more than 4 (per Yamaha) years old. Steel-braided Teflon lines are available, cost more, but are considered to be a lifetime replacement.

The caliper seals are also wear items, as are the master cylinder seals.

Stopping > going.

 

Thanks for the tips, I did try to use a clamp to push the cylinder in and it wouldn’t budge. Taking a look at the brake lines they definitely are out of date so I will replace those and I think the master cylinder as well.

Also just found out that one of the cylinders isn’t firing so looks like I have my work cut out for me.

Thanks again
Evan

 

email Len at info@xj4ever.com for parts

You do not need to replace the master cylinder or calipers. Both are rebuildable.
There are writeups in the DYI forum. If you can't find them let me know and I'll provide the links.

As far as the non-firing cylinder it could be something very simple as a corroded plug lead. Check for spark on that cylinder. The spark plug caps screw off. Look for green. The copper wires can be cut back by about 8mm to make a good connection. If that's not it then we can do some more diagnosis.

Read This First
The above link will get you started. Do the reading before starting on the work.
Please keep all questions about the machine in this thread (I can retitle it for you if desired). It makes it easier to follow your progress and avoid missing things that are clues to diagnosing interrelated systems.

Enjoy the ride. I'ts gonna be fun once you're finished with the refurbishment.

 

Fast forward a little while, I’ve now replaced the brake lines and rebuilt the calipers. The master cylinder screws were stripped so I bought a replacement.

Currently trying to bleed the brakes but been having difficulty. I can’t seem to get any pressure when squeezing the lever. Brake fluid comes out of the bleed screws on both calipers with no bubbles.

I have also bled the master cylinder at the top fitting of the brake line.

My thought is that there must still be air in the lines somewhere because there is zero resistance at the lever. Haven’t tried a vacuum bleeder yet but that seems a little pricey to buy if I can avoid it.

None of the brake line fittings are leaking any fluid, so I don’t think there’s a leak anywhere.

Any ideas?

 

You can tie the brake lever to the handlebar and leave it overnight, might work could be tiny bubbles in the fluid.

 

A couple of years back I was having trouble bleeding my calipers/master cylinder, one of the members suggested pumping fluid brake fluid up to the M/C thru the caliper. Worked like a champ!! I had spent a couple of hours pumping the M/C and not getting anywhere, back filled the calipers and M/C and had solid brakes in less than 5 minuets.
Good luck!

 

I’ll give that a go, see if it works.

 

There are a couple methods of getting the fluid to the point where the lever will finish the bleeding process and both are easy and inexpensive. I have used a syringe and clear bleeder hose with great success. Put one end of bleeder line over syringe opening with plunger all the way down into syringe and the other on the caliper bleeder nipple. Open the nipple then pull the syringe plunger out to create suction. Hold it there till you see the fluid coming out. The other ways I have done is just to suck it out with your mouth. There is little chance you will get any in your mouth as the fluid does not come out quick enough. just be sure it is a clean tubing. Has never failed for me.

 

If that dosen't work, go one step further.
Bleeding the XJ750 Seca Front Brakes
While it's written for the Seca 750, the last steps to get the air out can be applied to any hydraulic circuit.

 

Just a quick bit of advise after reading a previous post. Back filling the brake line does work very well and I have used it before switching to suction. The reason I switched was the last time I did it the line popped off and there was brake fluid EVERYWHERE! Cleanup took a long time and I had to do it quickly cause that brake fluid is caustic stuff! If you do try that method be sure you have very secure fittings.

 

It's actually good that it happened in the shop instead of on the road. The fitting would have likely popped under use anyway.

 

Well, actually I meant the bleeder line when back filling. The pressure can make it pop off if you're not careful.

 

I just filled my lines from below after rebuilding/cleaning the calipers. I discovered that too much syringe pressure can indeed pop the line off the bleeder and does indeed spray everywhere in a flash.

 

Ok, so I left the lever squeezed overnight and that didn’t work, so I tried backfilling from both calipers and that also didn’t work.

I also tried a gravity bleed which was unsuccessful, as well as using a syringe to make suction to bleed the calipers, which also did not solve the problem.

There is still no resistance at the brake lever at all.

The only thing I can think of is maybe the master cylinder I bought is faulty?? I’ll admit I bought it from eBay and it is not an oem replacement, but the build quality seems good and I would be surprised if that’s the issue.

Pretty stumped here.

 

I would hate to buy another master cylinder and that not solve the problem.

 

you have to think like a bubble, anywhere a bubble can go up it will. look at the wheel cylinders, if the wheel is to the left a bubble can get trapped in the right side cylinder, and visa versa.
watch the splitter and the angle of the line where it goes in the master

 

Yeah, could be a problem with the master cylinder cause it should not be that difficult. And you say you replaced the lines too, hmmm. You might try shooting some compressed air through them to be sure you have a clear path. The aerosol cans work best for this or if you have a compressor. If that shows the lines are clear then you might want to remove the master cylinder and disassemble. I know when I recently rebuilt the master cylinder on an older Ninja I made sure the internal parts were well lubricated with brake fluid, especially the plunger. And if for some reason that rubber gasket part of the plunger is reversed it will not work properly. And you put a crush washer on each end of banjo bolts, right? Just trying to think of anything that would cause an issue.

 

I did a search for this issue and included a couple links .... Maybe it will help.

https://www.xjbikes.com/forums/threads/86-xj700-brake-bleed-issue-resolved.118163/

https://www.xjbikes.com/forums/threads/this-brake-is-refusing-to-bleed.117322/

 

Yeah I bought a set of brand new stainless steel braided lines from galfer. And yes to the crush washers also.

Found a video on YouTube that shows how to test if the master cylinder is actually making pressure, so I think I’ll give that a go.

Supposing the lines aren’t clear, what solutions would there be to such a problem?