front master cylinder question

[cobrasneverdie]

Hey guys, here I am again with yet another question. This one concerns front master cylinder, I will be ordering one from mikes. I have a 76, but when I look at the one I want to order
Part #08-0265 - Master Cylinder Assembly - 16mm bore. - "Recommended for late dual disc Front
brakes on 1977-84 "XS650's or single front disc brake (1972-76 650's). Yamaha
OEM type. Complete with brake lever, brake light switch, banjo bolt and washers."

here is a cheaper one:
Part #08-0255
but it doesn't state anything about 1972-76 and I see no significant difference in the pictures.

Which one am I best to purchase?

I thought I'd ask cause lately nothing seems to be working and I don't want to re-order parts... I've been doing a lot of that, it's frustrating.

again thank you for the answers

 

[5twins]

You need to learn a bit more about your brake to understand what's happening here. Your older single caliper moves two pistons (and pads). The later calipers have only one piston that moves. That's why the 16mm bore #08-0265 works on yours or on a pair of the later ones. The #08-0255 only has a 13mm bore so won't work well with your 2-moving-piston caliper. It's for one later caliper which moves only one piston.

 

[cobrasneverdie]

5twins, thanks for the response, I guess I have more to research than I thought.. This sucks, this means I have to replace my front brake disk system to use either of those fmc?

I guess I have to purchase the Part #08-3000, which I really don't like the look of... ugh thanks man I appreciate the feedback

 

[5twins]

No, you don't need to replace it. Where'd you get that idea? You just need the right sized MC, one with a 16mm bore. Mike's sells several in that size, also several with 13mm bores. The 13's are too small for your application. The 0265 16mm bore MC will work fine if that's the one you like. The 08-3000 is too big @ 22mm. It's for 2 old style calipers.

Keep studying, you're still not getting it.

 

[shitsnack]

Hugh's Handbuilt stocks some nice front masters.
http://www.xs650.com/forum/showthread.php?t=26924

 

[cobrasneverdie]

thanks I see what you're saying now

 

[XSLeo]

I have done some testing on my bikes. My 75 had the old style two piston caliper. It had a 16 mm master.
I didn't really like the set up. Worked ok but the lever pull was a bit heavy and there was not much feel. A 14 mm master from a later bike improved the feel and eas of lever pull and increased the power of the brake.
Of the two you listed the 08-0265 being a 16 mm it will be the same as your stock master.
The 08-0255 being a 13 mm will improve the braking just a bit more than the 14 mm will. Just be carefull the first few miles. The increase in braking power takes getting used to.
I swapped all the brakes for the later style single piston calipers. The stock 16 mm caliper worked with two of the later calipers but it was a bit wooden. You had to pull the lever very firmly to get any braking but if you pulled just a bit to hard it locked the brake. Kinda like an on/off not progressive at all. I tried a 14 mm master from the later bikes. Very good, the braking power was increased as well as the feel.
When appling the brakes the brakes felt much more progressive. I could feel them better and could tell when they were going to lock before they did lock.
I have a 12.9 or 13 mm master that I tried with the two later single piston calipers. Very powerful. I used them that way for awhile but just couldn't adapt. Too powerful.
I tried the 12.9/13 mm master with just one caliper and it was very close to the feel and power of the 14 mm with two calipers.
I didn't like the 12.9/13 mm master, no adjustment on the lever like the stock masters.
I went back to the dual calipers and 14 mm master.
I wrote a thread explaining the way a brake syhstem works and how changes effect the power and feel.
I don't know how to link to it, but it's out there.
Leo

 

[cobrasneverdie]

thanks xsleo, I put the order through on mikes, I need to start putting my bike together before season is over.

I'll have to find your post you were talking about, it will definitely be a good read.

 

[gggGary]

This one?

Brake Upgrades?

 

[XSLeo]

Yes, that's the one.
Thank you gggGary for finding it.
I hope it helps people better understand how the brakes work.
Leo