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

[Tugboat]

<edit: was "Rear wheel doesn't spin freely when rear axle nut is tightened">

It's just one thing after another tonight!

Adjusted my chain, torqued the rear axle nut and now my back wheel doesn't spin freely when in neutral? Loosen the nut, spins fine. Not sure if it was like this before I initially loosened the nut to adjust the chain. What's going on here?

'76 750F

[Cqyqte]

I am repling to this based on the supposition that you are talking about your '76 CB750.  The two rear bearings are spaced correctly with a central spacer tube.  If either of the two bearings are not seated properly in the hub then the outer races are too far apart and when you torque the axle nut, it drives the center races of the bearing tightly against the center spacer which in turn cause the balls to press against the inner egdes of the outer races.  Remove the rear wheel and reseat the bearing on the brakeside, then loosen the retainer on the sprocket side and reseat the sprocket side bearing.  Re-assemble the wheel and try torquing the axle nut and see if that corrects the problem.

It is imperative that the brakeside bearing's outerrace is driven completely against the ridge in the hub.  Then when the sprocket side bearing is being set you support the brakeside inner bearing race when driving the sprocket side.  The impact of the sprocket side bearing on an unsupported brakeside bearing can cause the outer race to shift away from the ridge.

Sorry for the complex response, I couldn't think of an easier way of describing the issue.

[754]

 Make sure the "GreasyStepSpacer" is between the 2 bearings on the sprocket side...

[WhyNot2]

I have the same issue..............can't figure it out, hopefully we both learn something here.

I kind of loosened the nut back out alittle cause when tightened to torque value from the book, the castle part of the nut was too far in for the cotter pin to touch.

Wheel still seems tight, no side to side movement.

[madmtnmotors]

Make sure the "GreasyStepSpacer" is between the 2 bearings on the sprocket side...

This spacer goes BEHIND the sprocket carrier. It often "sticks" with the sprocket carrier when the sprocket carrier is removed and can fall off while moving pieces around. This spacer MUST be in place for the bearings and hub to work correctly and its absence will cause the condition you describe. 

I kind of loosened the nut back out alittle

AIEEEEE!!! The rear axel MUST BE TIGHT! 

[Xnavylfr]

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)

[MCRider]

Yeah you're missing a spacer. Or the bearings may be improperly seated. You didn't mention replacing the bearings.

Bottom line is: axle tightness should have NO EFFECT on how easy it is to spin the wheel. What i call the "spacer stack" dictates the width. This stack is made up of the center races of the bearings and the various spacers which all touch each other when properly assembled, giving a complete side to side "spacer" as one. The axle then passes thru the stack.

The axle nut, no matter how tight, cannot change the overall width of this stack, leaving the wheel free to turn on the outer races.

While checking the chain is always a good idea, it can't be causing the problem you're having with the axle nut threading too far onto the axle. This is evidence of a spacer problem.

[Tugboat]

Thanks guys.. I'm more disappointed than anything else. Just finished putting my FRONT end back together (new neck & wheel bearings, new fork seals, new tire, painted everying nice & pretty...) and was supposed to go ride the Cherohala(sp?) Skyway with @Spanner1 and some SOHC/4 boys from Northern GA this weekend. Not gonna happen now.

I assume I'll have to order new bearings, since I'll damage the old ones getting them out to check the spacer? Any other parts I'll definitely have to replace?

[madmtnmotors]

I assume I'll have to order new bearings, since I'll damage the old ones getting them out to check the spacer? Any other parts I'll definitely have to replace?

The spacer that is likely missing does not require bearing removal. If the bearings are removed, they can be repacked and reused if necessary. I remove and repack the bearings any time I press a used wheel into service. The dust seals can be gently pushed out of the bearing (I use a large, straightened paper clip from the opposite side) and the put back in after cleaning/packing. Sounds like a microfiche with circles and arrows is in order...

[MCRider]

Thanks guys.. I'm more disappointed than anything else. Just finished putting my FRONT end back together (new neck & wheel bearings, new fork seals, new tire, painted everying nice & pretty...) and was supposed to go ride the Cherohala(sp?) Skyway with @Spanner1 and some SOHC/4 boys from Northern GA this weekend. Not gonna happen now.

I assume I'll have to order new bearings, since I'll damage the old ones getting them out to check the spacer? Any other parts I'll definitely have to replace?

You shouldn't have to move the bearings to check the internal spacer. Just stick your finger in the bearing hole and if it feels a collar type thing that goes across to the other bearing, well its there.

The stepped spacer that goes behind/between the sprocket drive plate and the hub, is the one many of us are suspicious about.

#10 if this pic posts.

http://www.motogrid.com/pages/OemParts?aribrand=HOM#/Honda/CB750F_A_(78)_MOTORCYCLE%2c_JPN%2c_VIN%23_CB750F-2200001/REAR_WHEEL_%2b_DISC/CB750F-78-JPN-A/2Y134102F13410212A

[strynboen]

on my cbx,i have to put a shims behind the bearing..to take that pressure ..the spacer must have be kompresed over time..or po have done somthing vrong...its the only time i seen this problem
a tric to remove bearing in hveel...veld a bolt in the hole in bearing..then you can hammer it aut from the other side..

[madmtnmotors]

Thanks guys.. I'm more disappointed than anything else. Just finished putting my FRONT end back together (new neck & wheel bearings, new fork seals, new tire, painted everying nice & pretty...) and was supposed to go ride the Cherohala(sp?) Skyway with @Spanner1 and some SOHC/4 boys from Northern GA this weekend. Not gonna happen now.

I assume I'll have to order new bearings, since I'll damage the old ones getting them out to check the spacer? Any other parts I'll definitely have to replace?

You shouldn't have to move the bearings to check the internal spacer. Just stick your finger in the bearing hole and if it feels a collar type thing that goes across to the other bearing, well its there.

The stepped spacer that goes behind/between the sprocket drive plate and the hub, is the one many of us are suspicious about.

#10 if this pic posts.

http://www.motogrid.com/pages/OemParts?aribrand=HOM#/Honda/CB750F_A_(78)_MOTORCYCLE%2c_JPN%2c_VIN%23_CB750F-2200001/REAR_WHEEL_%2b_DISC/CB750F-78-JPN-A/2Y134102F13410212A

Ouch! The diagram almost looks like the spacer is outside the sprocket carrier. #10 is indeed the spacer in question. I'll break down a rear wheel assembly this evening and see if I can post some pics that might be more visually understandable. I've probably got a spare stepped spacer if it turns out yours is missing.

[bollingball]

I don't see how anyone could loose or leave out #10 or #12. Could #10 be in backwards?

                                          Ken

[Duke McDukiedook]

on my cbx,i have to put a shims behind the bearing..to take that pressure ..the spacer must have be kompresed over time..or po have done somthing vrong...its the only time i seen this problem
a tric to remove bearing in hveel...veld a bolt in the hole in bearing..then you can hammer it aut from the other side..

Or just get a blind bearing puller if you need to pull out the bearing.

[MCRider]

I don't see how anyone could loose or leave out #10 or #12. Could #10 be in backwards?

                                          Ken

I think that it will go in backwards and cause these symptoms. Been a while since I've had it apart.

[TwoTired]

It's just one thing after another tonight!

Adjusted my chain, torqued the rear axle nut and now my back wheel doesn't spin freely when in neutral? Loosen the nut, spins fine. Not sure if it was like this before I initially loosened the nut to adjust the chain. What's going on here?

'76 750F

I had this problem with my 78 Cb750F when I was getting it ready for Corbin.  It was missing #15.

http://www.cmsnl.com/honda-cb750f-750-super-sport-1976-usa_model490/partslist/F++10.html

[madmtnmotors]

I had this problem with my 78 Cb750F when I was getting it ready for Corbin.  It was missing #15.

http://www.cmsnl.com/honda-cb750f-750-super-sport-1976-usa_model490/partslist/F++10.html

That is the same spacer as the #10 spacer on the CB750K microfiche referenced above....

Going to take picts of the wheel assembly and spacers now.

[Tugboat]

Awesome! Thanks so much guys.

[Tugboat]

OK, some pix. There was a spacer on top of this that I removed. Don't judge... first time I've really looked at this

16" rim, btw.

[madmtnmotors]

Okay, I'm sorting the pictures and instructions, give me about ten minutes to put this together. Stay tuned...

[MCRider]

In the meantime think of the concept of the spacer stack. There has to be a continuous flow of spacer the diameter of the inside race that goes from one chain adjuster to the other.

[bollingball]

I thought TT was talking about leaving out this #15

http://www.motogrid.com/pages/OemParts?aribrand=HOM#/Honda/CB750F_A_(78)_MOTORCYCLE%2c_JPN%2c_VIN%23_CB750F-2200001/REAR_WHEEL_%2b_DISC/CB750F-78-JPN-A/2Y134102F13410212A

Ken

[madmtnmotors]

Here we go (from the rear) for CB750K8:

Fully assembled, sproket side:




Fully assembled, brake side:




Full assembly:




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




Reassembly, in order, from left to right:

Left axle adjuster goes on axle shaft:




Then the 25mm spacer:




Then the sprocket carrier:




THEN THE 42MM STEPPED SPACER. This links the bearing in the sprocket hub to the bearing in the wheel hub:




Then the sprocket carrier fits into wheel hub:




Then the brake hub (no spacer here):




Then the 35mm spacer outside the brake hub:




Then the right axle adjuster:




Then get the biggest wrench you can find, and crank-er-down:

[MCRider]

iTS #10 OR #15 depending on the fish. I introduced a 78F fish, not meaning to confuse things. Its the stepped spacer.

Madmtn has it documented though.

[TwoTired]

I thought TT was talking about leaving out this #15

http://www.motogrid.com/pages/OemParts?aribrand=HOM#/Honda/CB750F_A_(78)_MOTORCYCLE%2c_JPN%2c_VIN%23_CB750F-2200001/REAR_WHEEL_%2b_DISC/CB750F-78-JPN-A/2Y134102F13410212A

Ken

No. I gave the reference relative to the OP's bike in question and the link I posted.  The 78 F uses a different part list numbering.  But, the spacer function is the same.

Cheers,