Alternative to 75-76 dual disk 7/8' bore MC

[thibay]

Hi,

My 1975 european XS 650 1E1 front end will need to be rebuilt => both calipers (seized pistons), MC, fork.

I don't find any rebuild kits for this master cylinder. Mikexs sells a new complete MC for +100$.

Later XS's with dual discs has 16mm bore MC. How will it work on my stock setup ?

A lot of used later dual discs/MC are selling on ebay for cheap but I don't want to change my complete fork just for that.

Any advices on rebuild kits or cheaper alternative ?

Thanks,

Thib

 

[RFLIVES]

I used a zx10r radial master

 

[thibay]

Thanks RFLIVES, but this is somewhat too modern for my bike
Anything pre 2000 ?

 

[RFLIVES]

1999 ZX10R?

 

[arcticXS]

Hi!
Since your stock M/C is 7/8" or 22.2 mm, I assume you have the early type, 2 piston calipers. These were also used on the RD 350, with a 5/8" (15.88mm) M/C, in a single disc setup.

Now, I have a buddy with a -75 RD 350 (I have 2 of those myself...) His M/C was shot, and he needed a replacement. He ended up with a 1/2" Grimeca M/C, and says the brakes now are really great, better than stock. The smaller M/C gives higher fluid pressure, more braking for less effort.

Going from 7/8" to 16 mm is a bit bigger reduction than going from 5/8" to 1/2", but if you upgrade to good quality steel braided teflon brake lines (Aeroquip, Goodrich, Hel, etc) at the same time, I will most likely work fine, and give more braking for less force at the brake lever.

 

[gggGary]

No personal experience but going down in MC bore is usually a good thing. Here is a chart of MC vs. caliper with a description of what works from an acknowledged expert.
Vintage Brakes

 

[thibay]

1999 ZX10R?

Nice one

 

[thibay]

Thanks a lot arcticXS and gggGary.

I would never though that going down in MC bore could be better !
Of course I'm looking for braided lines, rubber ones aren't really cheaper.

I'll look for a cheap 16mm MC then. Which common bikes share this bore ?

gggGary, your link is worth bookmarking it

 

[thibay]

I spotted two interesting local ads. Both from Gixxers.

Can I keep the stock rotors with those calipers ? Or adapt the GSXR rotors on the XS ?

 

[thibay]

And there are Yammy MT03 controls. Don't know the bore yet but the look isn't too modern, I like it.

 

[gggGary]

I adapted SV650 rotors, the whole fork actually, on to an XS spoke wheel but it wasn't for the faint of heart. The Zookys have 5 bolt holes in the rotor on a different radius, the center bore matches. I migged the 5 holes shut and drilled 6 new holes in the rotor using an XS650 rotor and a wheel hub as a guide. Warning Will Smith I have not actually ridden on this set up, but I like how it looks! One serious issue is the shorter forks on the Suzuki's

View attachment 7837

There is some useful discussion of Zooky fork swaps in this thread. http://www.xs650.com/forum/showthread.php?t=8395

 

[thibay]

This front end suits it very well indeed ! And yes the rotor mod needs some skills and tools.

 

[gggGary]

You may need to watch clearance with the 4 pot Gixxer calipers, the extra depth of the back pistons may hit the spokes. The SV calipers just have front pistons and there is clearance.

 

[thibay]

Ok I might go to the MT03 controls. It's only 35€
But I doubt which calipers I have. Mine looks like the early type but placed behind the forks like the later models.

Do I need to source RD400-XS650 early calipers or later models xs650-750-850 ?

 

[XSLeo]

In 76 they put the calipers behind the forks. Same caliper as earlier. In 77 they went to the 35 mm forks and the single piston calipers.
Any single disc M/C from I think 72 up to 76 used a 16 mm M/C, I think all the Yamaha's from those years, XS or not used the same M/C.
If you want different calipers then get the early two piston calipers. They mount right on the fork. 82 mm ctc mount holes. The later calipers are one piston and mount On a bracket with 112 ctc mount holes.
Mike's XS lists rebuild kits for your calipers, #29-0019 $22 each, new pistons #29-0518 $22 each. He now has complete calipers also.
Master cylinder # 08-6009 Is a 16 mm and should work well with the dual caliper set up you have. Has the round reservoir, $55
Leo

 

[XSLeo]

The later XS750, XS850 and XS1100 standards use the same calipers as the XS650, the specials do not.
Leo

 

[MacMcMacmac]

I put one of these on a 650 Turbo and it really improved braking (along with braided lines).
Not bad for <$100. The one I bought was for a dual disc destup and had a 5/8" bore if I remember correctly.

http://www.partsnmore.com/parts/yamaha/xj650l/?filters[year]=1982&filters[page]=2

 

[XSLeo]

The 650 Seca turbo has as stock a 5/8 or 16 mm M/C That's what I had on my 75 with a 79 fork with later style dual calipers. Works ok, a bit wooden. The 14 mm from the 77 up bikes works very well.
Leo

 

[thibay]

XSLeo, the round reservoir M/C has everything. Affordable and correct look.

Tonight I'm going to see a complete XS1100 + title for 150€. Depending on its front end shape I'll probably go to a swap OR #08-6009 w/ rebuilt calipers & braided lines.

Thanks everyone for the quick answers !

 

[thibay]

Hey guys,

Just wanted to let you know I bought the XS 1100 for parts. I used its master cylinder and brake lines.

I got the pistons out of my original caliper by hooking them to the XS 1100 MC.
I just had to clean them, no need for a rebuild kit. Dust protectors are shot but I can live without them for a while.

Rubber lines aren't strong enough, I will need to go to braided lines as suggested but I still have a weak front brake now. Better than nothing

I rebuilt the forks (just cleaned and filled, no need to install new seals either) and the bike is on the road now

Here a video I took 2 hours ago: