Twinpot Brake upgrade on 78 Skunk

[Sarnath]

Are there any mounting brackets left?

I have an '85 GS550E which has dual rotors. I'd like to upgrade the calipers now and hold onto the spacer so that I can upgrade the rotors at a later time if I need to.
The rotor diameter of a CBR900RR is 296 mm according to http://metalgear.com.au/, however the diameter of my rotors is 260 mm from the same source. Will this kit still work? Do I need to get new rotors at the same time?

From metalgear.com.au for 1985 GS550E:
Outside Diameter: 260
BCD: 78
Thickness:5.0
Offset:21.5

Also, will the following calipers work?
From a 750:

http://www.ebay.com/itm/89-Kawasaki-ZX-750-7-ZX7-ZX750-F-Ninja-front-brake-calipers-right-left-/310911736314?pt=Motorcycles_Parts_Accessories&hash=item4863c899fa

http://www.ebay.com/itm/89-Kawasaki-Ninja-ZX-750-R-GPX-Front-Brake-Calipers-W-Lines-KH-/130880116077?pt=Motorcycles_Parts_Accessories&hash=item1e7910156d

From a 600:

http://www.ebay.com/itm/1989-Kawasaki-ZX6-ZX600-600-ninja-front-brake-calipers-/291182949845?pt=Motorcycles_Parts_Accessories&hash=item43cbdb35d5

http://www.ebay.com/itm/1989-Kawasaki-ZX6-ZX600-600-ninja-front-brake-calipers-/321684387443?pt=Motorcycles_Parts_Accessories&hash=item4ae5e23673

Thanks

[salty_monk]

Yes to brackets available.
Yes those calipers will work.
Yes you are correct on the 296mm rotor size.
You will need to do the rotors at the same time. The only other option is to use two rotors from a GS single rotor model such as the older GS550E or GS1000C etc. Those are 295mm & work fine but are very heavy...

[Sarnath]

Thanks for the quick reply! PM'd you about the brackets.

Will the following rotors work on my 85 GS550E? If so which would be recommended? I don't know if one is superior to the others in performance or if they're pretty much the same.

And I just want to confirm, but I'll be set for the upgrade with a pair of rotors, the bracket/spacer set, and a pair of calibers right? Assuming the brackets you have are steel which means I can use the original mounting bolts.

Thanks for the help!

CBR600F3:

http://www.ebay.com/itm/Honda-CBR600-CBR-600-F3-Front-Brake-Rotors-95-98-/251832488803?pt=Motorcycles_Parts_Accessories&hash=item3aa262d363&vxp=mtr

http://www.ebay.com/itm/Front-Brake-Disc-Rotor-for-Honda-CBR600F-CBR-600-F3-1995-1998-CBR900RR-1994-1997-/311211386068?pt=Motorcycles_Parts_Accessories&fits=Model%3ACBR900RR&hash=item4875a4e4d4&vxp=mtr

http://www.ebay.com/itm/Round-Front-Brake-Disc-Rotors-For-Honda-CBR600-F3-1995-1998-CBR-900-RR-1994-1997-/261656934029?pt=Motorcycles_Parts_Accessories&fits=Model%3ACBR900RR&hash=item3cebf7f68d&vxp=mtr

CBR900RR:

http://www.ebay.com/itm/1-set-Front-Brake-Disc-Rotor-FIT-Honda-CBR900RR-1994-1997-/171519541143?pt=Motorcycles_Parts_Accessories&hash=item27ef5c7f97&vxp=mtr

[salty_monk]

Pm back. Those Rotors look right. The RR ones you need to check Dia - some RR ones are larger dia than 296mm. If you are buying new get the ones with the 78mm PCD / BCD rather than 76mm, that way you only have to enlarge the holes to 8mm rather than re-drill between existing.

The spacer also acts as a drilling jig (bolt it to two existing 6mm holes using shoulder bolts & drill the 8mm straight through - with a drill press is best).

[shryke300]

Saltymonk, I know you must get tired of helping us all flounder through your upgrade! I am very happy with mine. I do want to ask for some measurement confirmations, though. The twin disk forks I got were a little narrow for some reason. I was wondering if you had some measurements to show how the rotor is to be centered in the calipers?

[salty_monk]

You should be able to see it by eye, just centre it within the body of the caliper.
with the 550 Rotors it isn't precisely central but it doesn't seem to affect anything - as long as the pads don't drag on one side (because you are so far off centre the slide can't compensate) then you should be fine.

Check bu by hand before riding it!

[Badger8v]

Can I purchase spacers only and can you send to the uk.I am running a usd gsxr fork on an RG500 and want to fit a gs hub as I fancy spoked wheels.

[salty_monk]

Send me an email/pm and we can work out if they're suitable. The GS hub is pretty narrow compared to the GSXR

[Sarnath]

Finally got around to putting the new rotors on and mounting the calibers and I ran into an issue. It looks like the rotor offset is at least 5mm too small.


The above picture shows the spacing when the rotor is up against the inside pad, I measured the gap between the spacer and bracket to be 5-6mm. If i try to tighten caliper mounting bolts any further it pulls strongly against the rotor. I don't know if I just messed up somewhere or if I need a greater offset for my bike. The bolts screwed into the caliper bracket are the original caliper bolts and the new bolt is an M8 by 45mm bolt as per your instructions in post #213. It seemed a little long when I was fitting it originally but then I realized those instructions where for the aluminum bracket which is thicker, it still clears the rotors though but i'll try to cut it down later.

My main question is, assuming I didn't make mistake somewhere can I add an additional spacer either on the hub or two spacers on the caliber mounting bolts? I can get custom spacers for the bolts pretty easily and if nessesary I can get a thicker hub spacer but I don't know if the final product would be strong enough.

I have several additional photos that might help clarify the issue, but I can't attach more than one per post. Let me know if I can supply any additional information.

Any help is greatly appreciated.

[salty_monk]

I have PM'd you an email address for more pictures. It may well be something specific to that model - I am not sure anyone else has ever fitted to that particular one.

Sure we can figure it out though!

Are the pistons fully retracted & pads installed in the pictures?

You can use photobucket to post multiple pictures to a thread - there are other similar services (free) too.

Cheers,

Dan

[salty_monk]

Well we sorted that out... We now know how to fit them to the 85 550E! No change in parts but slightly different configuration.

I do have some more brackets here if anyone is in need.

[Wobbler]

Hi all! Another upgrade installed to my GS1000G and it is working great! I had installed it sometime ago but got finally a change to go out for a test drive. I can't really compare it to the old brakes because I haven't driven with the bike that much, but it is a nice upgrade. I still need to take it to the inspector but it should be fine. Thank you Dan for the kit and all the help with it.

One question about the master cylinder. Are you using the stock master cylinder? Would it be good idea to upgrade it also?

[salty_monk]

I have used stock & I have used a couple of different ones from Kawasaki's. They are all similar. Stock was a little more wooden feeling from memory.

This is the one I am using now. Has mirror mount & adjustable lever - from an EX650

[shryke300]

Salty monk, thank you for your patience. I am trying to get my kit installed, but am having a very hard time getting everything to center. I would like to delete the speedo and am trying to use two mushroom spacers that are the same length... Still doesn't work! DO you or any others have any suggestions? If you need pics, just tell me what you want them of/what perspective.

[salty_monk]

Remind me of the situation, bike, fork etc. The equation should be pretty simple - put the wheel on the axle with no spacers. Centre the rim between the fork legs. Measure between the bearing face & the fork leg on each side. That's the length of spacer you need on each side.

When you get the rim central the rotors should follow therefore you then have to work out how far they need to be offset to centralise between the pad area on the caliper. In theory that distance should be the spacer that I gave you but if it's not (because you are mix & matching from memory) then I might be able to see a way around it. I have some odd sizes from early experiments somewhere on the shelf.