Topic: 1975 CB750 Rear brake hub help

[Hellcat]

Hello, I'm finishing up a custom cb750 build but am running into issues with the rear brake hub. The issue is that the outside of the hub rubs on the outside of the wheel like there is a spacer missing. Looking at the parts fiche it doesn't appear to have a spacer in there but if that's the case then does that mean i have the wrong brake hub for the wheel?

https://photos.app.goo.gl/unY1F3mqXIuGBVcD2

https://photos.app.goo.gl/KY0do9GHiQbCYqfJ3

https://photos.app.goo.gl/Wc4zPi7V3bPCP9rA2

[754]

This often missing,  the spacer betwern the sprocket carrier and wheel hub, check that.
 That spacer had a step on it.

[BPellerine]

looks to me like you have a dohc rear hub,they have that groove around them,they are that much wider than the sohc hubs,dont ask me how I know.bill

[Hellcat]

@754 If this spacer goes on the sprocket side how would it affect the brake hub spacing? How do I find this spacer, remove the sprocket holder?

@bpellerine looking at 1975 cb750 brake hubs on ebay I think you are correct. 

[Hellcat]

I took some measurements to see why the brake panel was rubbing and how much space was needed to correct:

1. Difference between brake panel surface being scratched 15.7mm and brake panel axle space 9.75: 15.7-9.75 =  5.95mm
https://photos.app.goo.gl/ko3CJzrpckULJ7It2

2. Difference between drum hub and bearing surface 7.6mm (needs to be less than the above 5.95mm measurement or it will rub)
https://photos.app.goo.gl/2xnaIFOL9OzDa6tf1

7.6-5.95 = 1.65mm.

So basically I'm 1.65mm short of hitting the bearing surface and preventing the rubbing issue. I have to get some things machined anyways and was wondering if there is any issue with machining a 3mm spacer to fit between drum bearing and brake panel to fix my problem? I'm helping my friend finish this build he started a year ago and everything is powder coated and re-laced on the wheels so I'd hate to have to start over.

My plan for spacer here (take a look at those scratches this has been rubbing for a while!): https://photos.app.goo.gl/iNhgg8bXawnebcd83

Input/advice/thoughts appreciated??

[Hellcat]

Got my 3 spacers installed today and all issues are fixed. 1 spacer inside the brake hub to keep the brake panel from rubbing and the other 2 to center the wheel and align the chain sprocket.

Figured out along the way I'm working with a 75-77 cb550f swingarm, late model cb750 hub, and (correct for the bike) 1975 cb750 brake panel all working together now!