Master Cylinder

Previous owner replaced the master cylinder with one which I can not identify. My brakes are getting spongier and I've done everything I could including rebuilding the callipers. By now I'm pretty certain my master cylinder is on it's way out, but without knowing which master cylinder it is, i can't order a rebuild kit.


A quick search shows 14mm as the typical bore size for an xj650 front brake but I can't find if that's standard for single or double calliper.


Could someone point me in the right direction? Thanks

 

What year and model is you XJ?

Did you replace the brake lines?
Original brake lines are mucho dangerous.
Putting braided stainless steel lines will increase stopping performance.

XJ4ever has everything you need for re-building caliper, master cylinder and replacement hoses/ hardware.

 

Stainless steel braided lines EBC performance pads. Clean and lube all sliders regularly. Had the rotors regrind but helped minimally. Dot 4 fluid

The Initial bite isn't that bad, main problem is as i grab harder, brakes are not biting any harder. Lever goes to the grip and bike is still moving along.
I have no clue what size my bore is or what size of a bore I should have.

 

1. get the right master cylinder
2. use Dot3 fluid
3. get rid of the rotors that are too thin.
4. do a rebuild of the correct master cylinder

 

I don't even know what master I have or what the right master is, and that's the main question I'm asking.
I'm using dot 4 which is fully compatible with dot 3, been using it for years on cars and other motorcycles with nothing but amazing results. ATE Type 200 is what I use
My rotors are not too thin. They are still within spec and not warped. It was ground for a clean smooth surface, didn't take any significant material off. And It's in specs after the grind
I took my master apart and things look good. No leaks or anything either. My guess is fluid is getting past the first seal and back up to the reservoir

So now I'm trying to figure out what is the "right" master cylinder. I'd prefer to get a reasonably priced relatively new master cylinder since I don't care about it being original OEM part as it's not a perfect collector bike. I can get 14mm bore and 17mm bore assemblies for $40. But I have no clue what size bore the original xj650 RJ had

 

Your master cylinder bore size would be dependent upon number of calipers single or twin? Do you have access to Haynes or climber manual to assist with sizing ?
Dot 4 should be fine for your brake system.

 

I have a master cylinder from a Maxim 650 (single caliper) sitting on my bench for a rebuild. It has a 14mm bore.

 

original size is always a good bet. it depends on the diameter of the master vs the diameter of the caliper(s) take a look here and see what you think
http://www.vintagebrake.com/mastercylinder.htm

 

RD337: Look in Chacal's many volumes for the stock bore diameter. I think he has original and aftermarket options for most XJ's and will indicate the bore diameter for your bike. As well, that chart Polock posted might offer the option to deviate from stock a little if you desire. I replaced my master this past winter, and even though my brakes had been great with new fluid, pads and SS lines, they got MUCH better when I put on a new master of stock bore. Only took one important stop this summer to prove that it was money well spent.

Polock: That's some useful brake data there. Thanks. I'm building up another bike, non-XJ, and that will come in quite handy.

 

I never quite understood how to find chacal's inventory details..... Occasionally I search the right words and something from him pops up, but is there an official database?

 

Click on "forums", scroll down just to "Marketplace", first on on the list is "xj4ever /Len Chacal contributing vendor " or something like that..... Anyway, he's the top of the list. You can also just email him at: info@xj4ever.com . Tell him what you need and he'll give you all the specific information.

Dave fox

 

If I recall correctly, you have a 1981 XJ750 Seca, and it uses that odd "remote-mounted" master cylinder (located on the headlight bracket):

17.46mm diameter bore (11/16th)


Other models:

Front Master Cylinder Rebuild Kits:

These OEM and aftermarket kits contain the typical main working “guts” of your master cylinder: the aluminum piston, its seals, return spring, spring cup (when used), piston boot and its retainer clip. Other parts needed to properly rebuild and original master cylinder --- the fluid level sight window, cover, cover diaphragm, cover screws or nuts, mounting clamps, fluid level sensor and hardware (when used), etc. are not included and should be ordered separate.

NOTE: before ordering your master cylinder rebuild parts, please take a moment to inspect and confirm that your bike does indeed have a factory original (for your model) master cylinder on it. After all these years….and so many previous owners…...there’s no telling what’s resting up there on your handlebars, and since rebuild parts are quite specific designed to work only with a particular style master cylinder ----- well, it’s best to be safe than sorry!

So here are the clues for original master cylinder identification:

XJ550 all North American models: the cylinder body will have the size 1/2 and the word NISSIN cast into it along the larger rear facing side of the cylinder body. Original (1981-83) cylinders will have the word NISSIN in all capital, block-style letters, while later “replacement” cylinders will have the word NISSIN appear as a stylized semi-script, with the two “s” letters layered on top of each other. Both types will accept all of the parts that we have listed below as fitting original master cylinders.

XJ550 non-North American models (dual-disc bikes): the cylinder body will have the word NISSIN cast into it along the larger rear facing side of the cylinder body, and have the size 5/8 cast into the forward face of the cylinder body just to the left of the fluid outlet port (where the brake line attaches).

FJ600 and XJ900 F, N, and FN models: the cylinder body will have the size 5/8 cast into large front face side of the cylinder body just above the fluid outlet port (where the brake line attaches), and the manufacturer name does not appear anywhere on the cylinder body.

XJ600 Seca II models: the cylinder body will have the size 14 (meaning a 14mm bore) cast into large front face side of the cylinder body, and the manufacturer name does not appear anywhere on the cylinder body.

XJ650 Maxim and Midnight Maxim North American models (single-disc): the cylinder body will have the size 14 (meaning a 14mm bore) and the word NISSIN cast into it along the rear face of the piston bore.

XJ650 non-North American (dual disc) models, XJ650RJ Seca, all XJ700, XJ750-X, XJ750RL, and XJ900RK and RL models: the cylinder body will have the word NISSIN cast into it along the larger rear facing side of the cylinder body, and have the size 5/8 cast into the forward face of the cylinder body just to the left of the fluid outlet port (where the brake line attaches).

XJ650 Turbo, 1982-83 XJ750 Maxim and Midnight Maxim, and all XJ750 Police models: the cylinder body will have the size 5/8 cast into it along the larger rear facing side of the cylinder body, and the word NISSIN does not appear anywhere on the cylinder body. The 1982 XJ750 Maxim cylinders have a small (1/4” diameter) hole in the base of the reservoir where the fluid level sensor wires exit the inside of the reservoir.

XJ1100 Maxim and Midnight Maxim models: the cylinder body will have the size 14 (meaning a 14mm bore) cast into it along the rear face of the piston bore, and the word NISSIN does not appear anywhere on the cylinder body. The bottom of the reservoir has a small (1/4” diameter) hole in where the fluid level sensor wires exit the inside of the reservoir.

If your master cylinder does not match the above descriptions, then we may not be able to assist you with rebuild parts for it…..there are an incredible number of both original and aftermarket master cylinders that were/are available, they all look somewhat the same, and they all may or may not accept nor function properly (or at all!) with component intended for use with the original master cylinder used on your bike!

 

Thanks for chiming in Chacal.

Previous owner swapped the front end over and I knew nothing about these bikes when I first bought it so naturally I thought he just swapped the headlight system to a round one.

I know I have some sort of xj650 front end and if I'm not mistaken, it's an xj650R which supposively came from europe...? It's got dual front callipers. And the master cylinder is definitely not the original one...

So it's been over a week since my last attempt to bleed it and for some reason it got a lot better. I'm guessing air was stuck somewhere. I could still use more umph
"XJ650 non-North American (dual disc) models, XJ650RJ Seca, all XJ700, XJ750-X, XJ750RL, and XJ900RK and RL models: the cylinder body will have the word NISSIN cast into it along the larger rear facing side of the cylinder body, and have the size 5/8 cast into the forward face of the cylinder body just to the left of the fluid outlet port (where the brake line attaches)."
Would it be safe to assume that I am supposed to have a 5/8" bore? so if I want a harder lever, should I go for 11/16" or more?

 

The 650r non turbo forks are also slightly farther forward than the 650 maxim. The triple tree clamps are specific to that bike.

The 650r is not just a European bike---- they came to the states for 1982.

 

Chaccal's catalog, let each section load then save it on your PC. So much faster next time you need it

 

I still say use dot3 brake fluid. I checked every single one of my mc caps and they all say to use only Dot3 brake fluid.

 

3, 4, and 5.1 are all compatable. The main difference between them is the boiling point. The higher the boiling point the more effective braking is under severe conditions (high altitude, panic stops, long downhill sweepers).

http://www.advancepetro.com/differentbrakefluid.htm

DOT5 is the devil and should not be used except in a vehicle that is stored more than it is used.

Dave, When our bikes were new DOT3 was the best choice because that supersceded DOT1 and DOT2, which were castor oil based fluids (DOT 1 and 2 have much lower boiling points and also do not absorb water; instead allowing water to pool in the system and flash to steam under hard braking).

 

water flash to steam in the brakes......yea baby, i'am in

 

yeah, well. When our bikes were new, we were supposed to use non-detergent dino juice......I'll still use that, too.

dave.

 

Dave, if you're talking about non-detergent oil you're misremembering. Detergent oils came into widespread use in the 30's, were taken off the civilian market during WWII, and went back into use following the war. I can't beleive that you like sludge in your engine.