Rear Disc Brake conversion for 1981 SH

molochnik

molochnik

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Tried doing multiple searches...and I can't imagine I'm the only person to attempt this, but can anyone tell me what I need to find - what model bike/parts - to convert my SH from a cast wheel and drum to a disc?

I *thought* there were models out there with a rear disc and laced wheel. I'm just not sure what I should be shopping for.

From doing some research, I presume my bike to be an SH model; the VIN starts with a 4M4...but this is only a presumption. The bike came to me with two different side covers and one said "Special II" but there are things that tell me otherwise.

Thanks in advance
 
molochnik said:
I cannot go to a laced wheel with a disc brake...using XS/TX parts?
Click to expand...
Right; there's no "simple" route but it can be done with some parts bin searching and a bit of machining.
The trick is finding a spoke hub that will accept a small enough sprocket to work with XS650 gearing.
This one from a GS1000
LH rear detail.jpg
right rear detail.jpg
 
molochnik said:
Tried doing multiple searches...and I can't imagine I'm the only person to attempt this, but can anyone tell me what I need to find - what model bike/parts - to convert my SH from a cast wheel and drum to a disc?

I *thought* there were models out there with a rear disc and laced wheel. I'm just not sure what I should be shopping for.

From doing some research, I presume my bike to be an SH model; the VIN starts with a 4M4...but this is only a presumption. The bike came to me with two different side covers and one said "Special II" but there are things that tell me otherwise.

Thanks in advance
Click to expand...

I'm right in the middle of parting out an '80 XS650SG, it has the cast mag wheel with the rear disc. Can't help you if you're wanting a spoked wheel setup, but I can sell you all the parts that you'd need to convert using stock Yamaha parts, including the frame (with title) and swingarm. Let me know if you're interested in that approach. I'm in Carson City, NV
I'm also a big fan of the Yamaha XS750 Specials, I've owned two of them. All of the US market XS750's used cast mag wheels, with shaft drive and rear disc, but I learned that Yamaha made spoke wheels for the XS750, with rear disc, for their home market (and possibly) other markets than the US. I've only seen photos of the shaft drive/spoked rear wheel. With that being said, I'm wondering if Yamaha made spoked rear disc brake wheels for the XS650 in other parts of the world?
 
molochnik said:
I saw your edit. It appears from your link and what you're telling me above that I cannot go to a laced wheel with a disc brake...using XS/TX parts?
Click to expand...

Added some pics and info to the Link i posted on the swap

As gggGary posted......He is the man who has done this
 
RJames said:
I'm also a big fan of the Yamaha XS750 Specials, I've owned two of them. All of the US market XS750's used cast mag wheels, with shaft drive and rear disc, but *I learned that Yamaha made spoke wheels for the XS750, with rear disc, for their home market (and possibly) other markets than the US. I've only seen photos of the shaft drive/spoked rear wheel...........* With that being said, I'm wondering if Yamaha made spoked rear disc brake wheels for the XS650 in other parts of the world?
Click to expand...

*Not on the XS650. No Spoke wheel disk brake.

*Yes its called a GX750.....76 GX750 had a single exhaust and the headers all curved to the side.......Don't know if the XS750 Specials had the spokes but the Standards did
GX75008.jpgGX75007.jpg GX75001.jpg GX75005.jpg GX75010.jpg
 
If one was so inclined you could do an Omar’s conversion kit with a factory front hub laced to an 18” rim of your choice, right? But that an awful lot of $$ to accomplish the task.
 
I appreciate all of the input. I was hoping for a fairly simple junkyard-sourced conversion. I've been using some Talon hubs with 17s but the bike is too low; find myself dragging the frame.
I'm looking to use 18s or 19s front and rear to get it off the ground some more. The rear brake has been a PITA to get sorted so perhaps a "Special" rig on the rear is how I'll go.
Thanks again for all of the input...you've all saved me some head scratching regarding what is what
 
If your looking for an 18" rear wheels with a disk brake set up then an RD 400 rear wheel can be made to suit with minimal cost and the hub also has rubber damper in the hub.

Stay with Mags and have 18" front and 18" rear

This was sent to me from "slide" at the 650Garage,
RD 400 rear wheel conversion01.jpg RD 400 rear wheel conversion02.jpg RD 400 rear wheel conversion03.jpg RD 400 rear wheel conversion04.jpg
 
Last edited:
I am going to change the Storm to spoke wheels. Picked up a set of 75 XS wheels,rear drum. I could not find a Yamaha 36 spoke disk rear wheel. Some Suzuki GS and Kawasaki KZ had them. Pick a 79 KZ750 wheel. It has a 20mm axle the same as XS650. Other than spacers should not be a problem. More later.
 
gggGary said:
The KZ750 twin rear wheel can be made to work but it is a HEAVY SOB.
Click to expand...

Yeah...that's why I was hoping to have laced wheels with a rear disc. After lots of whittling I managed to get the bike down to 285 lbs with a constant loss lighting system. The bike that Skull posted is awfully sexy, and I have a set of RZ350 wheels I used for the bike's first iteration but they are also wicked heavy. I think the set of supermoto wheels I have on it weighed half as much.
I'd like to keep it real light - the bike really moves with all the weight shaved off.
 
gggGary said:
Since you already have the talons, change the rims to 18x3? or buy 18" Talons?
Click to expand...

Why?...I'm probably just looking for a cheaper alternative :)
The Talons are vestiges from my YZ250 supermoto endeavors. That said, your suggestion is a sound one
 
I should also add that the width of the Talons makes it tough to find a suitable rear caliper. All the calipers I've got sitting around hit the spokes. I've converted some 4 pot calipers to twin pots with less than stellar results in terms of braking power. That's why I was originally hoping there was a "stock" rig I could use to avoid the figgering and fabrication...I'm just getting lazy and cheap for the latest iteration of my "experiment" bike. :)
 
If the calipers hit the spokes, can you add spacers to move the rotor and caliper out far enough to clear the spokes?
Leo
 

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