Topic: Rear wheel does not spin freely - '76 CB750F

[Tugboat]

Stepped spacer is there. Hmmmmm..

[Pecantree]

Thanks Madmtnmotors!!!!!!!!!!!!!!!
I was wrestling with this this evening and this is EXACTLY what I needed
Now, back to TT's dilemma!

[lucky]

Make sure you have 1/2 inch up/down play in your chain, simple problem, but most times the simplest problem is the least obvious!!!

Xnavylfr(CHUCK)

1/2 inch up and down when the riders weight is on the bike.
BTW get the wheel and bearings correct before you even put on the chain.

[madmtnmotors]

Stepped spacer is there. Hmmmmm..

Now verify that the spacers are the correct length, and then verify that the spacer between the bearings in the wheel hub is in place as well.

[madmtnmotors]

Also, the F model is a little different animal. The assembly I used in the photos was a CB750K8. I can break down the rear wheel on my 76' CB750F for a one-to-one comparison if necessary. Are you using the stock setup with the rear disk brake, or has it been converted to drum brake on the rear? I believe the stock wheel was 18"(?) so we might have to focus on the entire asssembly to determine that all of the proper parts are in place to accomodate the conversion to the 16" wheel, such as hub width, spacer lengths, etc.

I may be able to tear down the 76' 750F rear wheel assembly this evening, unless I run out of want-to, then it may take a day or two and I'll post the same series of photos for the F assembly.

[Tugboat]

Pix from the disc side



Best I could do this morning.. inside. Spacers seem to run the length of the shaft.


As far as I can tell, it's a 16" rim on the stock '76F hub. Bearings were replaced at some point - thus the drill marks in the retainers? Still running disc brakes in back.

[754]

 IF you CHANGED the rear sprocket carrier(proper way to line up 77/78 engine sprocket)..you may have used the earlier shorter greasyspacer..you need the longer one in there.. that may be it

[Tugboat]

Funny you should say that.. I was just on another thread talking about the fact that it's a '77K motor on a '76F frame and I'm not sure if the PO swapped out the carrier or not. How can I measure it to see if it's correct? Also, what are the dimensions for the stepped spacer, and others?

[754]

 The wide part of spacer is longer, and should show in those posted pics. IF THE GREASE is soft, put carrier/spacer into hub, INSERT FINGER, then move up and down if its SHORT, it will move about 3/8 inch..10mm

[madmtnmotors]

Funny you should say that.. I was just on another thread talking about the fact that it's a '77K motor on a '76F frame and I'm not sure if the PO swapped out the carrier or not. How can I measure it to see if it's correct? Also, what are the dimensions for the stepped spacer, and others?

Fully disassembled. Parts from left to right:
-Left axle adjuster
-25mm spacer
-Axle (above)
-Sprocket carrier (above axle)
-42mm STEPPED SPACER, THIS IS LIKELY THE CULPRIT
-Brake hub
-35mm spacer
-Right axle adjuster
-Axle nut



I didn't measure the stepped portion. Can give greater details later if needed.

[Tugboat]

Did some research on the spacers.. documenting here.

Stepped spacer different (76F) 42605-300-000; (77K) 42605-393-000 
Sprocket side spacer same (76F) 42311-425-870; (77K) 42311-425-870 
Brake side spacer different (76F) 42311-357-010; (77K) 42313-393-000 
Internal spacer different (76F) 42620-392-000; (77K) 42620-ME1-405

Will do some mearsuring when I get home. Thanks for all your help guys!

[WhyNot2]

I learned something 2day, by reading and watching this thread. And man, am I glad.

So, Thank You Tugboat brother. You and the fine people who rang in probably saved my life. I have been riding it like this back and forth to work, for the last 2 weeks, since I got it legal.

I would have never known, until the unimaginable would have happened.

Or not, cause no investigations would occur.......they would have figured, old guy on old motorcycle crashes.

Well, as you can see from the pics I'm missing something.

Number 11, and is not available.................................so, I'm dead in the water.

Actually, after further investigation, I think I'm missing # 8 the collar......darn POs.

So, if anyone has one and wants to part with it...........................?

http://www.servicehondapsn.com/fiche_section_detail.asp

[madmtnmotors]

I learned something 2day, by reading and watching this thread. And man, am I glad.

So, Thank You Tugboat brother. You and the fine people who rang in probably saved my life. I have been riding it like this back and forth to work, for the last 2 weeks, since I got it legal.

I would have never known, until the unimaginable would have happened.

Or not, cause no investigations would occur.......they would have figured, old guy on old motorcycle crashes.

Well, as you can see from the pics I'm missing something.

Number 11, and is not available.................................so, I'm dead in the water.

Actually, after further investigation, I think I'm missing # 8 the collar......darn POs.

So, if anyone has one and wants to part with it...........................?

http://www.servicehondapsn.com/fiche_section_detail.asp

You are correct. The stepped spacer you have is #11 and goes behind the sprocket carrier against the wheel hub. You are indeed missing #8 that goes on the outside of the sprocket carrier. If someone can tell us what a 75-76K (same part, but different than 77/78) spacer length is, I might have one laying around.

[Tugboat]

OK. Drumroll.......

Sprocket-side spacer: 25mm
Stepped spacer: 33 mm
Brake-side spacer: 23mm



Also, the space between the "deck" of the carrier and the sprocket mounting surface is 26mm.

[madmtnmotors]

OK. Drumroll.......

Sprocket-side spacer: 25mm
Stepped spacer: 33 mm
Brake-side spacer: 23mm



Also, the space between the "deck" of the carrier and the sprocket mounting surface is 26mm.

Need to know how far apart the back of the bearing in the sproket carrier is from face of the bearing in the hub. Put the stepped spacer in place and slip the sproket carrier into the hub, and reach through the axle opening (center of the outer bearing) to check for in and out movement of the stepped spacer inside. I'm guessing there's going to be quite a gap there. The 77/78 has an extra 10mm of sproket offset, and the stepped spacer for a 77/78 is about 10mm longer than the one you have.

Or you could take some measurements and do some math...

OMG A MATH QUIZ! 

 

Additional note:
The deck to sprocket height on the 77/78 is 36mm so it sounds like you've got the "F" model sprocket carrier. Do the front and rear sprockets appear to align properly?

[Spanner 1]

Kinda lost at his point !... but if someone posts the dimensions of the correct 3 spacers, I'll look at whatever wheel spares I have 

[Tugboat]

I reassembled the sprocket side with the stepped spacer in place, and there is a slight lateral movement when you put your finger in the hole and move it up and down (TWSS)... probably due to it not being completely snugged-up. Minimal - if any- gap. So it would seem that the spacers are correct for the hub & carrier, correct? In which case, what else could cause it to bind?

[754]

 Your pic shows short spacer, it will only work with 76 or down sprocket carrier, you cant run that with a 77  or later motor and be lined up.. not sure what sprocket carrier you have,................................................................................................,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

[madmtnmotors]

Your pic shows short spacer, it will only work with 76 or down sprocket carrier, you cant run that with a 77  or later motor and be lined up.. not sure what sprocket carrier you have,................................................................................................,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

The 26mm mounting height of the sprocket matches the 76' model.

[Tugboat]

For sure... So I'm thinking that I need a '77-78K hub/carrier. There's a guy in town who has a powder-coated 16" 77/78 rear wheel. At the very least I'm heading over to his place to take some measurements. Hopefully he'll sell me the whole shebang and I can just swap out tires. Sure would make life easier. BTW he rides this:
Imported from Germany.. probably 1 of 10 made. Badass.

[CycleRanger]

Pix from the disc side



Best I could do this morning.. inside. Spacers seem to run the length of the shaft.


As far as I can tell, it's a 16" rim on the stock '76F hub. Bearings were replaced at some point - thus the drill marks in the retainers? Still running disc brakes in back.

That rust is disconcerting.  There's been water in there. And the bearings have likely been stressed by the incorrect spacer stack.
You should consider new bearings while you're going through this exercise. 

[Tugboat]

Absolutely. Did you see the pics of the retainers?!? Destroyed! Shame that it took me this long to notice this terrible setup, but thanks to the generous help of this forum we'll get it straight.

[754]

 I didnt see all the shavings is that flanged spacer dragging against the reatainer?..it looks like it..run a straight spacer or switch it with the other side or replace it...

[madmtnmotors]

Absolutely. Did you see the pics of the retainers?!? Destroyed! Shame that it took me this long to notice this terrible setup, but thanks to the generous help of this forum we'll get it straight.

Tug,
    I'll break down the 76' CB750F rear wheel and measure the spacer lengths, carrier height, bearing to bearing width @ the hub, etc... and post the dimensions and pictures here. I've got an unmolested 76' F here that should settle it since it looks like you've got the whole setup from the 76' F.

[madmtnmotors]

Here ya go:

Fully assembled, brake side:




Fully assembled, sprocket side:





The spacers:
Sprocket side=25mm
Stepped spacer=33mm
Brake side=23mm (22.5 actually, close enough)
Sprocket to carrier deck mounting height=26mm




Distance from the outside of the left hub bearing to the outside of the right hub bearing (the height of the two hub bearings plus the spacer in the hub)=137mm (5-3/8")
(watch the vernier caliper, mine topped out and 133mm and I first thought I had hit the depth)




And finally, a picture of the back of the sprocket carrier for sags:





Looks like you've got all the correct parts for the 76F hub assembly. There are only a few possibilities left that I can think of:

*The sprocket carrier bearing is not seated fully into the sprocket carrier (increasing the gap between the sprocket carrier bearing and the hub bearing, in effect making the stepped spacer too short)
*The spacer between the bearings in the wheel hub is too short (hard to imagine, but anything is possible)
*The bearing on the brake side of the hub is not seated fully, allowing the bearing on the sprocket side of the hub to be recessed too deep (again, increasing the gap between the sprocket carrier bearing and the hub bearing, in effect making the stepped spacer too short)
*One or more of the bearings may not be correct (too thin)
*Are the 76F and 77F wheel hubs the same? If not, what is the difference? Could the wheel hub be from a later model? Would it make a difference?

You may be able to shim the stepped spacer at the bearing on the wheel hub side to get you by, but I would want to figure out the problem eventually. If I was going to make a shim I would use 20 or 24 ga stainless (galvanized sheet metal would probably work too) and cut the O.D. a little smaller than the O.D. of the hub bearing, and cut the I.D. very close to the O.D. of the axle.