Successfully converted my 1977 GS550. I did things a little different than standard went with a W800 master (12mm bore), MD1124LS 320mm Rotor and an EX500 caliper. The brake master was a bust, but the rotor worked out rather nicely. It’s the No drill original fork option that has been asked after many a time in this thread.
As some of you know salty_monks bracket has been successfully used on single disc GS550 or GS750’s to fit a 310mm 1998-99 CBR900RR rotor. The issue with using this rotor is pad overhang and you must drill it. BCD is correct, but holes are for 6mm hardware and The brake pad needs to be chamfered. The pads will touch each other as they wear. A potential alternative noted during the initial development was a Honda NT 650 or 400 bros rotor is 320mm, has the same BCD, offset, and was intended for M8 hardware like the GS. Not only does it solve the pad overhang issue (https://imgur.com/U91id2G) you don’t have to drill it. The rotor bolts right on and you can even use Hondas bolts (90105-KV0-700); they are same thread as the GS hubs. The only issue is that early speedo shields are too short to use without a rotor spacer, the Hondas rotor bolts felt too short to use with a spacer I reused the bolts I already had. But if you have a later model with a deeper speedo shield you likely won’t have to run the spacer and could use shorter bolts. With spacer, https://imgur.com/nKuejZY, and without https://imgur.com/1Q7RWtm
There are a couple of issues with this rotor, mainly price and availability. As far as I can tell very few NT BROS are in North America, saw one in Vancouver BC classified, couldn’t tell if it was an import or not. It’s very unlikely to find a used rotor. EBC and Metal gear (model number 21-079-A-GL) do make new rotors; I only saw them in Australia or Europe. When I asked an EBC distributor in the states, they said the EBC MD1124LS was discontinued but I neglected to check if that was just for the US, seem to be plenty on eBay at present. Price is going to be the other limiting factor the rotors are $200-300 shipped vs $130 for a single Arashi CBR900RR rotors. You end up spending around $70 to avoid drilling and chamfering pads, if you’re buying new.
Master cylinder was a bit of a bust. I was unable to find a rebuild kit for my master so I wanted something I could get parts for. The W800 and W650 both use a 12mm master, that looks the part, but it just doesn’t push enough fluid for 2 finger braking, pinky and ring finger got in the way. worked ok with 4 fingers but I switched back to the 14mm the bike came with for now. Another annoying feature of this master is a 34mm bolt spacing handlebar clamp, $34 clamp from Kawasaki. Most clamps have 32mm bolt spacing, I ran out of patience trying to find one and jury rigged it with a triple tree handlebar clamp from my bin of spares. Worked well enough to know it wasn’t usable.
Brake caliper came off a EX500, not much of note. If you’re redoing pistons and seals with OEM part look for a Suzuki rebuild set (59100-01831). It’s $75 for both pistons and all the seals vs $190 piecemeal from Kawasaki. The pin and piston seals are about the same price Kawasaki or Suzuki if your pistons aren’t corroded or you’re switching to stainless pistons, it’s not as big of a difference.
As for pads, I just went with a cheap NOS OEM pair I think for a concourse
The new rotor is 3lbs lighter than the original. 6.6lbs vs 3.6lbs
Calipers were both 3lbs.
This is an album of the previous photos:
As some of you know salty_monks bracket has been successfully used on single disc GS550 or GS750’s to fit a 310mm 1998-99 CBR900RR rotor. The issue with using this rotor is pad overhang and you must drill it. BCD is correct, but holes are for 6mm hardware and The brake pad needs to be chamfered. The pads will touch each other as they wear. A potential alternative noted during the initial development was a Honda NT 650 or 400 bros rotor is 320mm, has the same BCD, offset, and was intended for M8 hardware like the GS. Not only does it solve the pad overhang issue (https://imgur.com/U91id2G) you don’t have to drill it. The rotor bolts right on and you can even use Hondas bolts (90105-KV0-700); they are same thread as the GS hubs. The only issue is that early speedo shields are too short to use without a rotor spacer, the Hondas rotor bolts felt too short to use with a spacer I reused the bolts I already had. But if you have a later model with a deeper speedo shield you likely won’t have to run the spacer and could use shorter bolts. With spacer, https://imgur.com/nKuejZY, and without https://imgur.com/1Q7RWtm
There are a couple of issues with this rotor, mainly price and availability. As far as I can tell very few NT BROS are in North America, saw one in Vancouver BC classified, couldn’t tell if it was an import or not. It’s very unlikely to find a used rotor. EBC and Metal gear (model number 21-079-A-GL) do make new rotors; I only saw them in Australia or Europe. When I asked an EBC distributor in the states, they said the EBC MD1124LS was discontinued but I neglected to check if that was just for the US, seem to be plenty on eBay at present. Price is going to be the other limiting factor the rotors are $200-300 shipped vs $130 for a single Arashi CBR900RR rotors. You end up spending around $70 to avoid drilling and chamfering pads, if you’re buying new.
Master cylinder was a bit of a bust. I was unable to find a rebuild kit for my master so I wanted something I could get parts for. The W800 and W650 both use a 12mm master, that looks the part, but it just doesn’t push enough fluid for 2 finger braking, pinky and ring finger got in the way. worked ok with 4 fingers but I switched back to the 14mm the bike came with for now. Another annoying feature of this master is a 34mm bolt spacing handlebar clamp, $34 clamp from Kawasaki. Most clamps have 32mm bolt spacing, I ran out of patience trying to find one and jury rigged it with a triple tree handlebar clamp from my bin of spares. Worked well enough to know it wasn’t usable.
Brake caliper came off a EX500, not much of note. If you’re redoing pistons and seals with OEM part look for a Suzuki rebuild set (59100-01831). It’s $75 for both pistons and all the seals vs $190 piecemeal from Kawasaki. The pin and piston seals are about the same price Kawasaki or Suzuki if your pistons aren’t corroded or you’re switching to stainless pistons, it’s not as big of a difference.
As for pads, I just went with a cheap NOS OEM pair I think for a concourse
The new rotor is 3lbs lighter than the original. 6.6lbs vs 3.6lbs
Calipers were both 3lbs.
This is an album of the previous photos:
The brackets work with a nt bros rotor. (Honda equivalent P/N is 45120MN8000)
Edit:
took a 1982 GS650 speedo shield (suppose any of the later models should work) cleaned and re-painted it. fits nicely, ended up shaving another 1/2 lb off the front end once I removed monks disc spacer
https://imgur.com/W9nZoHg
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