Topic: cb750 rear hub difference

[trav72]

What is the difference between the 750 rear hub from a 69-76 vs. a 77-78 besides the sprocket carrier being a little wider?

[trav72]

With all of the knowledgeable people on here no one knows the answer?

[bryanj]

69-76 DRUM 77-78 DISC

[754]

The brake backing plate may be different? The brake torque arm i think is different. hubs are probably the same..anyoneone have a partsbook to check #s?

 The rim & spokes are different ..17 inch.

[moham]

69-76 DRUM 77-78 DISC

1978 cb750-F is a disc, but 1978 cb750-K is still drum...no?

[trav72]

I thought there were still drums on 77-78.  Am I mistaken?

[moham]

I thought there were still drums on 77-78.  Am I mistaken?

There is a link to the Honda Shop Manual in the Faqs for the 1978 cb750 both K and F models. In that manual you will see that the F model came stock with rear wheel disc brake and the K model came stock with drum brake set-up. Unless I have lost my mind (distinct possibility), I believe that I'm giving you reliable info. Moham.

[mustangcar]

yeah 77-78k are rear drum, with the beefy 630 chain,i know the spacers on the side of the hub are different -everythings different,i don't know what it takes to respoke an 18" wheel to a77-78k 17-inch hub,since the 77-78 hub is wider--custom spokes?? these wheel changes confuse the sh## out of me

[trav72]

yeah 77-78k are rear drum, with the beefy 630 chain,i know the spacers on the side of the hub are different -everythings different,i don't know what it takes to respoke an 18" wheel to a77-78k 17-inch hub,since the 77-78 hub is wider--custom spokes?? these wheel changes confuse the sh## out of me

I hear that!  I have a 78 swingarm, axle w/spacers, sprocket carrier....I just need the hub if it is in fact a drum.  I'll then have that laced to a 16" rim.  Then I can work on getting that all mounted up to my 550.  I'll just have to figure out what offset front sprocket I need....I'm hoping just 10mm.

[754]

use the 77/78 carrier it will give yousoewhere around7mm or more.

I am not totaly convinced that the 7 & 8 has a different hub. I can try to measure the width at the spokes later today, hope someone does that to a 7 or 8 so we can compare. I am thinking the only way the hub is wider is iff they also went to wider shoes.

[trav72]

I do have the 77/78 carrier.  I'm just trying to figure out if the hubs are different or if I can use the 77 carrier with an earlier hub.

[merc2dogs]

 internal spacer is different, one is slightly longer. So as long as you have the correct spacer it works ok.

 There are subtle changes in the hubs themselves over the years, but mostly cosmetic.
The only way I noticed it was by lacing wheels on a couple of my bikes so I looked at  acouple of my other ones and only two out of five hubs metched

ken.

[754]

77/78 carrier will definitely work on earlier hubs, but make sure you got the right spacer inside.

[trav72]

I guess I'm not to familiar with the 750 hub but what spacer are you talking about?  I've got the axle with spacers, sprocket carrier and swingarm.  If I were to buy a 74 750 complete hub that would not work without this inside spacer from a 77/78?

[754]

The brake drum has bearing and the carrier has one bearing.
A greasy spacer goes between thie carrier bearing and one bearing in the hub. This prevents the bearing from excessive side loads when you tighten the axle.

This spacer, can, will, and does fall out when working on the wheel. It is often misplaced or left out which will lead to bearing failure or worse.

[Keveen]

I have a 1978 Honda CB 750 K with a 1973 motor in it. Since the rear sprocket carrier is 10 mm wider. many years ago I had to put a cycleX 46T rear offset sprocket offsetting it 10mm inwards in order for the front and rear sprocket to line up. I switched from 630  to 530 chain and sprocket‘s because there was no offset available for 630 chain. I now want to put on regular sprockets and chain because I am changing to 17-18T front sprocket and 48T rear. No offset 48T to be found. I bought a 1973 sprocket carrier to swap into the original 1978 hub.My question is, can I swap a 1973 rear sprocket carrier into the 1978 rear sprocket hub? I know the Cush Drive rubbers on the 1969 -1976 are different then the 1977-78’s. I’m hoping I don’t have to buy a whole rearwheel as I am on a super tight budget.I already have the new sprockets chains as well as in 1973 rear sprocket carrier. Has anyone ever done this swap?

[seanbarney41]

It will work fine...be sure to get the wheel spacers for the 73 as well.  Especially the one that fits between the wheel and the sprocket carrier.

[robvangulik]

Here's a pic of the carriers side by side...

[Keveen]

Swapped my 1978 cb750 sprocket carrier to 1973 carrier.( I have a 1973 motor in my "78. front sprocket on '78 motor sticks out 10mm wider) 73' sprocket carrier is 10mm less wide than 1977-78's. you need to machine off 10mm off inside sprocket carrier axle spacer. I added 3 washers that add up 10mm along with original brake side axle spacer. I test fitted  rear wheel with '73 sprocket carrier using original outside axle spacer. it lines up perfectly with front sprocket. I am using 530 chain and sprocket. I get the shortened inside carrier spacer tommorow. I'll take some pics as I put it together.
The spacer on the right in the pic is the inside sprocket carrier spacer. The smaller diameter end fits inside sproket carrier bearing. It's the one i'm getting the larger diameter end trimmed 10mm . The spacer on the left is for the outside axle brake side . it is 10mm short ,therefore the 3 added washers to make up the 10mm .Hope this will answer some questions about swapping sprocket carriers on a 1978 cb750 to a 1973 carrier if you have a 1969-1976 motor in your '78. I'm new a new member from Canada

[seanbarney41]

really good clear info, thanks for posting