Author Topic: Rear wheel does not spin freely - '76 CB750F (Read 26184 times)

Tugboat · « **Reply #50 on:** March 12, 2012, 11:54:52 AM »

OK, so I plan on at the very least replacing the bearings and making sure they are correctly seated. I guess that's the cheapest/quickest option, and if it doesn't work I'm only out $30 for the bearings.

I'm going to have to deal with my offset issue as well, though. I'd like to get a sprocket carrier from a 77/78 and install it on my 75/76 hub. But do I need to get the stepped spacer from a 77/78?

Tugboat · « **Reply #51 on:** March 12, 2012, 03:10:07 PM »

I was about to pull the trigger and pick up a 77K carrier and a stepped spacer from a 77 750K so my sprocket alignment problem is solved. Then I saw a picture of the two different carriers next to each other and realized that my swingarm ('76) might not accomodate the extra 10mm offset. I checked the parts fiches, and the other three spacers are the same.. only the inner stepped spacer is different.

42311-425-870 sprocket side spacer
42620-392-000 inner spacer
42311-357-010 brake side spacer
42605-300-000 stepped spacer (76 750F)/42605-393-000 (77 750K)

So will the assembled wheel (incl spacers & chain adjusters) fit in the 76F swingarm? Or would I need a swingarm from a 77/78 bike?

madmtnmotors · « **Reply #52 on:** March 12, 2012, 04:58:04 PM »

Quote from: Tugboat on March 12, 2012, 03:10:07 PM

So will the assembled wheel (incl spacers & chain adjusters) fit in the 76F swingarm? Or would I need a swingarm from a 77/78 bike?

I can measure the width of the 76' F swingarm and the width of the 78' F swingarm (I have an example of each). Remember, the K and F swingarms are different in that the brake stay arm on the K (drum) mounts underneath, while the brake stay arm on the F mounts on top of the swingarm (disk) so if you were going to change swingarms it would have to be from an F model. I'm done for the evening, so it would be tomorrow at the earliest.

Tugboat · « **Reply #53 on:** March 13, 2012, 10:21:21 AM »

Well, I looked and the 76F hub is different from the 77/78K hub.. I bet the latter is wider. In which case that rules out me being able to just put the different carrier/stepped spacer on my 76F hub and (even with a different swing arm) being able to line it all up correctly without further modification.

It looks like what this is coming down to is two options:

(1) CycleX offset rear sprocket (if it clears) and new bearings on the setup I currently have. Would also need new 530 chain & front sprocket. Cost: ~$200

(2) 77/78 Comstar rim/hub, along with a new tire, new sprockets, new bearings/retainers, new chain & installed on a 77/78F swing arm. Cost: ~$450

754 · « **Reply #54 on:** March 13, 2012, 10:41:43 AM »

The late sprocket stuff fits in the earlier wheels, 530 sprocket bolt on. The most you need is sprocket carrier, greasy spacer, make outside spacer maybe. You may be able to use original swingarm. At any rate swingarm, a sprocket carrir/spacer.. well within 200 bux or less range..

Tugboat · « **Reply #55 on:** March 21, 2012, 11:27:15 PM »

Ugh......

After all that, here's the culprit. Didn't notice until tonight.

Anybody got a decent 75/76F swing arm?

madmtnmotors · « **Reply #56 on:** March 22, 2012, 05:47:42 AM »

Quote from: Tugboat on March 21, 2012, 11:27:15 PM

Ugh......

After all that, here's the culprit. Didn't notice until tonight.

Anybody got a decent 75/76F swing arm?

Is that bent? I would think you could straighten that. Also, to verify that the swingarm is the culprit, I would assemble the rear axle components seperately from the swingarm. Use some washers or other spacers so you can cinch down on the axle nut and verify that there are no other issues with your "hub stack" (the combination of all the bearings/spacers/hub/etc EXCEPT the swingarm). By removing the swingarm from the equation you can confirm your diagnosis.

754 · « **Reply #57 on:** March 22, 2012, 09:22:03 AM »

That swingarm looks like it should "pull flat under torquing", the early ones probably wont. Your trimming the sprocket made no sense to me, but does if the arm is bent.
Try lining your axle to the marks on it (not always exact) and then measuing centre of axle to centre of swingarm pivot... a lot of eyeballing required here, but should point out if its obviously bent.

Tugboat · « **Reply #58 on:** March 22, 2012, 11:07:54 AM »

It is bent, and does probably "pull flat under torquing".. but the pressure isn't evenly distributed to the bearings/spacers etc - ie it's tighter at the front than it is in the back, and that's why my wheel doesn't spin freely. My theory at least..... Picked up another swing arm on ebay for $20 in pretty good shape and we'll swap it out and see if that fixes it.

Also note that I'm not using any trimmed spacers or anything off a 77/78 bike to rectify the alignment issue. Instead I'm going with the offset sprocket from CycleX and using stock 75/76F swing arm/hub/carrier etc.

Spanner 1 · « **Reply #59 on:** March 22, 2012, 11:25:27 AM »

The saga continues... would drive a man to the drink.... well a few beers at least

WhyNot2 · « **Reply #60 on:** March 22, 2012, 11:57:15 AM »

Well, after my initial post of having the same issue, I have found that I am missing the outside collar.

PO had apparently lost it and put the step spacer on the outside, which made it look like everything was ok.

Have been trying to order one, have called all kinds of stealerships, and have found it discontinued.

Have had to work Saturdays, so have not had time to make it to one of the two salvage yards we have near this area.

But, once I do, I'll be back up again.

Thanks for letting my hang out, I've learned alot about the rear wheel get up on these bikes.

MCRider · « **Reply #61 on:** March 22, 2012, 01:37:03 PM »

Don't let that swingarm distract you. i will repeat: If the spacer stack is complete and proper, it doesn't matter how tight the nut is, or I'll add, how bent the SA is, you won't get the symptom in the original post.

Tugboat · « **Reply #62 on:** March 24, 2012, 01:31:08 PM »

Inner hub spacer:

Part number is the same for the 77F Comstar I have so I'll pull that apart and see if its spacer is in better shape.

754 · « **Reply #63 on:** March 24, 2012, 08:41:31 PM »

If the ends are fine just push the centering tabs back ib place, it looks useable...

WhyNot2 · « **Reply #64 on:** March 25, 2012, 05:37:38 AM »

Got to the salvage yard the other day and got the collar. The guy that runs the yard is in his 70s and doesn't open the yard anymore, so, he does all his work thru the internet.

Well, I told him I only live 20 minutes away, so he said he'd get the part and it will be in his mail box at his house.

So, I went there and got it, and left 7 bucks, cause he said I didn't have to pay him anything.

The collar works great and now the bike feels more stable on the road, and I feel more confident.

Thanks to you Tugboat for asking the ?'s and madmtnmotors for the in-dept pics and everyone else who rang.

thrutheframe · « **Reply #65 on:** March 25, 2012, 06:10:52 AM »

I've been watching this unfold as part of my program to learn as much as I can about 750's before I really start working on mine. I'm doubtful that the "bent swing" arm is the issue since it has nothing to do with free spin of the wheel. That being said, yes if it were racked enough to interfere with the spacer stack it could cause this I suppose. I have no idea what the issue is and I hope it IS the swing arm anomoly.... I know the frustration of thinking that I have an issue nailed down then replacing the part to find out it wasnt the problem.

Keep posting madmtnmotors I'm dying to know how this turns out.

754 · « **Reply #66 on:** March 25, 2012, 10:18:54 AM »

budflite try to get the thicker spacer under the nutr if the adjuster piece gets dished fcrom tightening axle nut, they dont slide as easy...

MCRider · « **Reply #67 on:** March 25, 2012, 11:46:34 AM »

Quote from: 754 on March 24, 2012, 08:41:31 PM

If the ends are fine just push the centering tabs back ib place, it looks useable...

Agreed. the end pieces are just there to hold it in place long enough for you to get the axle thru. After that they are meaningless. As long as the spacer itself is OK, looks like it is, run it.

754 · « **Reply #68 on:** March 25, 2012, 11:51:21 AM »

During bearing removal, unlees you are real good at it (or use an internal gripping puller), them tabs will often get pranged up...

thrutheframe · « **Reply #69 on:** March 29, 2012, 04:33:09 AM »

What happened?? Tugboat I'd love to know how this turns out.

WhyNot2 · « **Reply #70 on:** March 29, 2012, 05:15:48 AM »

Quote from: 754 on March 25, 2012, 10:18:54 AM

budflite try to get the thicker spacer under the nutr if the adjuster piece gets dished fcrom tightening axle nut, they dont slide as easy...

I got one, thanks. Been riding it to work everyday, rolls real smoothly now.

Thanks for all the help.

Tugboat, hope you git'er up and going.

NCSUEngineer · « **Reply #71 on:** March 29, 2012, 09:15:25 AM »

I was having this same problem despite having all of the assembly pieces. Them problem I had was when i fulled seated both the brake side and sprocket side bearing - the bearing spacer was so tight against the inner races that the bearings would barely spin. The assembly procedure was as follows:

1) Install sprocket side bearing and install retaining ring.
2) Flip wheel - insert bearing spacer
3) Install brake side bearing as far as it would go.

The result was the bearings not spinning and tightening the axle nut caused it to bind more and more as I tightened it.

If i installed the bearings in the reverse order..the sprocket side bearing retainer would not sit flush with the housing when tightened.
Either way - the bearings bound.

The only way i could fix this was to install the bearings and leaving a small gap between the bearing spacer. Doing this allowed me tighten to axle nut down as tight as I wanted with no binding. Bike runs good so far..

MCRider · « **Reply #72 on:** March 29, 2012, 09:22:26 AM »

Yes you discovered the "floating" bearing. You should install the retained bearing in all the way and run the retainer down on it. Then you install the other side but only down to where it just touches, or not quite, the internal spacer, as you did. Then when you tighten the stack down the inside race of the floating bearing becomes part of the bearing stack, and the outside race of the floating bearing finds its own home after a brief run in period.

No bind, or only an imperceptible amount, which will disappear after run in.

The way you had it first, assuming you were driving on the outside race of the floating bearing, had things in a bind. They probably would have worked their way out but in the meantime the outer race was not lined up with the inside race, putting the balls in a bind.

Tugboat · « **Reply #73 on:** March 29, 2012, 10:14:58 AM »

My balls have been in a bind for a few weeks over this issue LOL!!!

So, here's the outcome. New bearings installed along with the 10mm offset rear sprocket from CycleX. My brake drags a little.

http://youtu.be/gq-CEXohlG4

<<BAH!! How do you embed Youtube clips?!?>>

NCSUEngineer · « **Reply #74 on:** March 29, 2012, 11:19:27 AM »

Quote from: MCRider on March 29, 2012, 09:22:26 AM

Yes you discovered the "floating" bearing. You should install the retained bearing in all the way and run the retainer down on it. Then you install the other side but only down to where it just touches, or not quite, the internal spacer, as you did. Then when you tighten the stack down the inside race of the floating bearing becomes part of the bearing stack, and the outside race of the floating bearing finds its own home after a brief run in period.

No bind, or only an imperceptible amount, which will disappear after run in.

The way you had it first, assuming you were driving on the outside race of the floating bearing, had things in a bind. They probably would have worked their way out but in the meantime the outer race was not lined up with the inside race, putting the balls in a bind.

Good to know. It just goes against your intuition. In lots of machinery applications you preload regular ball bearings against each other in either a "Back-to-back < >" or "face-to-face > <" configuration. Back-to-Back is generally preferred as it makes a much stiffer bearing arrangement - its also why there is a correct and incorrect way to install your steering head bearings as tapered rollers HAVE to be preloaded to work correctly.

Regardless - thanks for the peace of mind MC!

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Author Topic: Rear wheel does not spin freely - '76 CB750F (Read 26184 times)