1100 Master CYlinder ID........

In my never ending quest to spend outrageous sums of money and time on my XJ650J (1982), I have been gathering up the parts needed to convert it to a dual front disc brake system. Got the forks & tubes & brakes off a '82/'83 XJ750, and recently bought a used master cylinder off e-bay from an '82 XJ1100 (since many people on this forum recommended that m/c as the be-all and end-all of factory Yammy master cylinders).

So I got it in, and in comparing it to the XJ750 master cylinder that I got with the used brake system, I notice that this XJ1100 master cylinder has a SMALLER reservoir than the one on the XJ750? Is that right? Is there any markings/casting or ID numbers on the factory master cylinders to tell which one is which?

Thanks.............

 

Dual master cylinder should have 11/16 embossed on the bottom. Standard single is only 9/16 or 14mm. Reservoir size between the two is often the same and interchangeable.

Probably a nissan unit.

 

Hello my friend, when you say "embossed on the bottom", where are you referring to? Both the 650, 750, and (supposed) 1100 master cylinders have a series of numbers cast into the outside of the plunger barrel, facing the driver. The 1100 cylinder has "14 6 T 1" cast there, the 750 cylinder has "5/8 6 T 3". Can anyone compare to theirs or interpret the meaning of these numbers? BTW, the reservoirs are not interchangable on these units, they are cast as an integral unit with the master cylinder..........

On the XJCD I can find the factory Yamaha PART NUMBER for the different master cylinders, but how does a person do a correct "in the field" determination of what master cylinder they actually have?

 

Chacal, the 14 on the 1100 cylinder implies to me that it is 14mm and is probably off a single disc system. Almost exactly the same as yor 5/8 one.

Bear in mind I am in Aussie and some parts I see come out specifically for the australasian market so they may be slightly different.

I have one off my 550 in the shed and it has 14mm embossed on the underside. When I converted to twin disc setup it came with an 11/16 master cylinder. All my XS1100's also have 11/16 MC's for dual discs.

I'm guessing that the MC you bought might have been an unsuitable replacement on the 1100 it came off.

Unfortunately, I don't think Yamaha actually made any brake MC's so you are unlikely to find any Yamaha part numbers on them.

Back to your original question re reservoir size. The capacity of the fluid it can hold is not too important as the fluid will only go up and down about 1mm during normal use. As you know it's more important to have an MC bore with a big enough displacement to activate both discs.

Got any pics of your 1100 MC?

 

xj 1100 only operate one disc with hand lever. The other front disc is tied into the rear brake pedal.

 

Ah, now that would exlain the smaller MC

 

Wow! That's the most insane thing I've heard.....but looking at the factory diagrams on bikebandit, seems to be true. DOesn't that make for some, errr.......INTERESTING braking at times?

 

It was a design used by the big bikes in the early 80s. Seemed some bright guy thought it would be better biasing for the heavier machines. Check out the 83-85 GL1200s, they have them too. We were told not have students practice controled rear wheel skids with these bikes.

 

Does anyone know how to remove the brake light switch from the master cylinder? It seems like one of those chinese box puzzles.........

 

It has two barbed ears that must be depressed through the square holes on either side of the switch mounting hole. Be gentle, they break rather easily as PBR_Street can attest. Replacement switches are available (XS switch will work) but hot glue gun will also hold it in place should you break the barbs off.