Replacing Rotors with XS1100 sloted rotors

Just a bit of info on the twin disk conversion. The chrome hose bracket can be obtained from the XS 500. That bike was a single disk but it was located on the other side so all the hardware is opposite the 650.
 
Just to throw in my .02 worth. The XS1100 Specials used a leading axle fork and the smaller rotors. The same with the Xs750 and XS850. Get parts from a standard model. The calipers are the same as the XS650.
The brake calipers on the leading edge forks are very different. The mount with a through bolt, back to front into the forks. Can't use them.
I'm not sure on the thickness if any of the XS750, 850 or 1100 used the 5 mm thick rotors. I think they used them on the lighter bikes. The bigger heavier needed the extra mass for heat dissipation. The lighter bike didn't have this problem.
I have a 7mm set of slotted rotors on the 81 and 5 mm slotted rotors on the 75. The 5 mm are much lighter. Better than 25% lighter.
Both bike stop very well. I use the stock 14 mm Master cylinder on the 81. I just bought and added one of those $27 Chinese masters sold on Ebay. It has issues, Not as nicely finished and the mirror mount is right hand thread so the stock right side mirror won't fit.
I do have a metric tap and die set, wonder if I can rethread the mirror or the master.
A stock lever fits and works, just no hole in the body for the return spring.
Leo
Do you know if the XS 1100 or XS 850 or even XJ 1100 rotor will fit on the front of a 1975 without any modifications??
 
I don't think any of those later rotors will work on a '75 because the offset is different. They only work on '77 and later 35mm forks with the later type single piston caliper.
 
I don't think any of those later rotors will work on a '75 because the offset is different. They only work on '77 and later 35mm forks with the later type single piston caliper.
Got ya!
Meaning they won’t bolt up to the hub or they won’t fit somewhere else. I have Morris mags on my bike so it’s not like they’re mounting up to the stock wheel, if thats is the issue you’re referring to
 

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The early rotors have more offset so you will need a fairly thick spacer to center an XS11 rotor on the caliper.
Somewhere in the neighborhood of 10mm, and that creates another problem, the rotor will no longer be centered by the hub flange.
 
Got ya!
Meaning they won’t bolt up to the hub or they won’t fit somewhere else. I have Morris mags on my bike so it’s not like they’re mounting up to the stock wheel, if thats is the issue you’re referring to
XS1100 rotors fit 1977 and later XS650 bikes without any modifications. XS750 and XS850 rotors are smaller, so no go.
 
The early rotors have more offset so you will need a fairly thick spacer to center an XS11 rotor on the caliper.
Somewhere in the neighborhood of 10mm, and that creates another problem, the rotor will no longer be centered by the hub flange.
Ahhh i see. May as well just leave it then as least regarding the front one. Now my rear is warped so im trying to source one for that. Again this is a Morris Mag setup and the rotor on the rear now is a 10.5in in diameter rotor. Anything off the top of your head that would fit??
 

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Ahhh i see. May as well just leave it then as least regarding the front one. Now my rear is warped so im trying to source one for that. Again this is a Morris Mag setup and the rotor on the rear now is a 10.5in in diameter rotor. Anything off the top of your head that would fit??
not 100% but the front rotors from an XS750 or the stock XS650 special rear rotors? 267mm IIRC
267 Millimeters (mm)=10.51181 Inches (in)
 
Ahhh i see. May as well just leave it then as least regarding the front one. Now my rear is warped so im trying to source one for that. Again this is a Morris Mag setup and the rotor on the rear now is a 10.5in in diameter rotor. Anything off the top of your head that would fit??

PS: XS1100 SPECIAL rotors are thinner than XS1100 standard rotors. IMHO a good thing.
A good thread on all of this here: https://www.xs650.com/threads/need-a-replacement-front-rotor-1976-c.58133/
I think the problem is I have a Morris mag so it’s going to be dealing with that as well as an early 70s bike. Nobody else has this set up so it’s hard to get sound advice.
 
The offset difference is more like 5mm, not 10 .....

Offset.jpg


Offset2.jpg


Easiest solution for you would probably be to just drill holes in the discs you've got. That's all I do, although I did swap on a couple 5mm thick discs from an SR500 simply because I had them laying around. They are supposed to be better for handling because they're lighter (results in less unsprung weight) but honestly, I don't notice any difference. What I did notice is they heat up more and faster. It's never been an issue, like causing brake fade or anything like that, but since they have less mass, they don't dissipate the heat as well.

A stock later 7mm thick disc I drilled .....

NewWheelMounted6.jpg
 
The offset difference is more like 5mm, not 10 .....

View attachment 325941

View attachment 325942

Easiest solution for you would probably be to just drill holes in the discs you've got. That's all I do, although I did swap on a couple 5mm thick discs from an SR500 simply because I had them laying around. They are supposed to be better for handling because they're lighter (results in less unsprung weight) but honestly, I don't notice any difference. What I did notice is they heat up more and faster. It's never been an issue, like causing brake fade or anything like that, but since they have less mass, they don't dissipate the heat as well.

A stock later 7mm thick disc I drilled .....

View attachment 325943
Well, the problem is the rear rotor now that I have attached the Morris mag is warped and that is a 10 1/2 inch, 7mm rotor. Every time I spin the wheel on the center stand it catches halfway through the rotation, so I’m pretty positive its warped. I like the idea of going with a thinner SR 500 rotor but I’m just not sure if the offset will fit the rear Disc brake conversion that I currently have. Thoughts??
 
If anyone knows your Morris/XS650 brake setup, it’s Michael “Mercury” Morse at 650central.com. He’s also Vintagebrake.com.

You may want to give him a call.
 
No, the 5mm SR disc has the same offset as the 7mm disc, so it wouldn't fit. When Yamaha made the 5mm discs, they took 1mm off each side, not 2mm off the front or back. The disc has the same center line, and same offset to it as the 7mm disc.
 
If anyone knows your Morris/XS650 brake setup, it’s Michael “Mercury” Morse at 650central.com. He’s also Vintagebrake.com.

You may want to give him a call.
I went to his webpage, and I clicked contact us and page will not load. And there is no phone number on his site anywhere. Do you happen to have a phone number??
No, the 5mm SR disc has the same offset as the 7mm disc, so it wouldn't fit. When Yamaha made the 5mm discs, they took 1mm off each side, not 2mm off the front or back. The disc has the same center line, and same offset to it as the 7mm disc.
gotcha. I guess I’m just gonna be stuck Trying to resurface this rotor getting rid of the warpage. Not much available.
 
Seeing this 10-y/o thread being resurrected gave me hope. Been thinking about putting cross-drilled rotors on the front. And this thread came just in time.

I don't think any of those later rotors will work on a '75 because the offset is different. They only work on '77 and later 35mm forks with the later type single piston caliper.
Dang, just my luck.
But all hope isn't lost. I have a program (that I made) to design fanning drill patterns so I can plug in some numbers and print out a sheet to drill out my '75 rotor.
 
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