early xs master cylinders

[DougXS2]

I've got three master cylinders to choose from for my 72 xs2 and need help i.d.'ing them...

two of them, I know, are the stock model; round resevoir, large round cap, etc. both need rebuilding.

the third one, I thought, was from a '73 xs650 (tx650?) and should be the same but the res and cap are both about 1/4 in. smaller? everything else is identical, light switch, etc. so I'm pretty sure its a yamaha xs650 from some year?

my question is, when did they change the sizes and is this smaller one cheaper/easier to find a rebuild kit if it needs one?

I could probably use it as is, except for the inner bellows or baffles in the fluid res. It appears the previous owner made the bellows from a piece of innertube? are replacements from this part available and what year would it be listed as?

 

[BigJimmyW13]

Pictures?!?.........

 

[DougXS2]

I'll try to do that....with a ruler for reference.

 

[KevC]

DougXS2
similar thread HERE
It may provide some useful information for you
Kev

 

[DougXS2]

thanks Kev. that does help somewhat...

guess I was really wondering; did they make two different sized round MC's and does anyone have a spare bellows/diaphram for the smaller of the two?

 

[XSLeo]

I don't think the size of the resivoir cap means much. The bore size is whats important. The bore size should be marked on them. Usually on the inside where it sets against the handle bar. All the ones I have are marked 5/8 I assume this is in inches. 5/8 th's inch is 16 mm's.

 

[DougXS2]

the cap size only matters in that the diaphram that fits the larger one is too large for the smaller resevoir. and I need to find a replacement diaphram for the smaller unit.

 

[XSLeo]

I did a little checking.
72+3 used a 366-25850-02-00 with a 360 or 306 -25854-00-00 diaphram
74+5 used a 735-25850-00-98 with a 360-2584-00-00 diaphram
76 used a 360-25850-31-00 with a 360 or 306 -25854-00-00 diaphram
They all used the same rebuild kits 1AO-W0041-00-00
The parts list don't refer to the size of the cap.
Why they list two diaphrams for the 72+3 and the 76 and not the 74+5 is your quess.

 

[XSLeo]

Maybe some of the folks can measure thiers and tell us what years had what size. I just have to find the one off my 75.
I have one from a 72 or 73 that measures about 51.5 mm across the threads, no cap.
still looking for the 75.

 

[XSLeo]

Found it. 75 is about 48 mm across the threads, 56 mm across the cap.

 

[DougXS2]

sounds like I have 2 older units and 1 75ish one....

the larger of these two is the 72, just like you said Leo

do they still make the diaphram for the 75 style MC's or is that something I'll need to round up used?

 

[XSLeo]

You can try a dealer with the part numbers I listed.
There are a few online parts places that may have them. Yamatopdog is one place. You can try puting Yamaha parts in your search engine and check the places it lists.
I'm sure some one will suggest a few places to look.

 

[DougXS2]

What do you think the difference is between the 360 and 306 prefixes?

 

[XSLeo]

That's the $64,000 question.

 

[musicman]

If anyone knows of a rebuild kit for a XS brake master cylinder please let me know. I ordered one from yamatopdog ($80) and it was not the right one. They told me that a rebuild kit is not available for the XS cylinder. Thanks! musicman

 

[XSLeo]

Music man If you look in post #8 I listed the factory part number for the rebuild kits. All the early ones used the same kit up to 76. If you use this number to crossreference with you should get the right kit.
The later models 77 up used kit # 535-w0041-60-00.
I like to cross reference part numbers using the parts list at www.babbittsonline.com
You can searh by looking up the part by make , year and model. You can also search by part number. when you search by part number it will list what years and models of bike the part fits.
Like with the 1A0-W0041-00-00 kit, fits 72-76 650's, the 80 TZ125, 76-77 RD400, 73-75 TX500, 73-75 RD 250 and 350's.
The 535-W0041-60-00 Fits the 77 up 650's, the 81-82 TZ250, the 76 up SR500, the 78 up XS400.
Babbitts list them both at $71.87. Their list says they have them, I would call to order just to be sure they are in stock.

 

[XSLeo]

Doug, As I was on Babbitts I checked for the 75 daiphram, they list it at $6.08, again call to order to ensure in stock.