Topic: Rear wheel sprocket

[kixbox]

Hi - I am reaching out to the community for some thoughts on what is happening and what this could be?

I was doing some cleaning around the bike (CB750k 1978) and noticed something odd around the rear wheel sprocket side - see pictures.  Does anyone know what this is? and should I be concerned? I am in the process of taking the back wheel out to check the rear brakes but did not have plans to go too deep. 

Any advice would be greatly appreciated.

[Steve F]

Looks to be bearing grease seeping past the seal.  You should look at replacing the seal and repacking the bearing(s).

[kixbox]

Thanks Steve - a lot. 

This is the first time I ever take a wheel off any thing let alone a vintage motorcycle (it was fun and felt manly) - even messaged the wife to share the moment. 

Jokes aside: what does 'repacking the bearings' mean? sorry for the super basic follow up question. 

Also, I snapped a few pictures of the inside for additional context - see below.

[BobbyR]

Your bearings are shot and you should not be riding on them. Those are ball bearings and today roller bearings are the norm.

[kixbox]

Thanks BobbyR. 

If its not too much trouble, can you suggest a link to what I should be buying to correct this?

[BobbyR]

These are fairly common bearings. All Balls is a brand that make kits.  https://www.bikebandit.com/aftermarket-parts/motorcycle-wheels-and-final-drive/wheel-parts-accessories/all-balls-wheel-bearing-kits/p/20235?b=3054163&CRTP=psc&gclid=CjwKCAjw3cPYBRB7EiwAsrc-uUAFJzz7VKxD_vWr6Em0wfuvzluyzITvDTW7N2IkjjIWGFpEoK6CVRoC0bEQAvD_BwE

[kixbox]

Thank you. 

I think I now need to learn the how-to.  Do you think it can be done by a beginner who is a fast study?

[BobbyR]

It is not difficult, there are certain tools you will need. you will need an electric drill and drill bits. There are how to videos and some good posts on this site. The search function is down again so you can google it.

[kixbox]

Thank you again. I’m on the hunt.


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[754]

If the wheel did not have a lot of sideplay, and not making noise they are probably  ok.
Repack or replace..

[kixbox]

Thank you.  Since I have it off the bike - I think replace is the way I'll go.  looking up some posts/vids on the forum on how this is doable. 

[kixbox]

One last question: where can I order CB750k parts? it is overwhelming when I do a search.  Any suggestion from my canadian friends as I live in Canada.

[BobbyR]

You can probably get the bearings from Amazon or Ebay or any of the Online parts dealers. Just google  CB750 rear wheel bearings.  There is nothing special about these bearings, they are commercially used bearings and guys have gotten them from bearing supply houses. 

It is a total waste of time to try to repack rusted out old bearings. I know where those thought come from since that was my Fathers way, good thought, but a waste of time. There are several videos on the web for replacement. Here are some quick tips:

When the bearings come in out them in the freezer and leave them there until you are installing them.  They will shrink.

There is a spacer in the center of the hub with 3 wings at each end. Bend it it out of the way, it was only used in manufacture and not load bearing.

There is a retainer that screws into the center hub.  There are staking dents in that retainer that deformed the metal so  jammed the retainer in place. You need to drill them out with the proper sized drill bit.  Don't be timid drill them out.

You can go to the hardware store and get a straight bar with several holes drilled in it used for bracing wood. Stanley makes them. Get two proper sized screws and nuts. Put the screws through the holes that line up with the holes on the retainer, put the nuts on the screws to hold them in place. That is as good as any spanner wrench and really cheap.

Put the protruding screw screws into the holes and roataete it left and right until the retainer comes loose and just spin off the retainer.

Once you are ready to put the new bearings in. Heat the hub with a heat-gun or hair dryer until it is pretty hot. Take the bearings and races our of the freezer and they will essentially just drop in since the aluminum in the hub had expanded and the bearing steel has shrunk. Get everything seated and you put the retainer back on the hub with your tool.   

You can re stake the the retainer with a punch or apply loctite.

[kixbox]

That is awesome detail, thank you!!

I ordered what I need and will start the process once everything comes in, in the meantime, I will clean the wheel and everything. 

Last question: it seems to me that the 6304s bearings are in good condition.  Its only the sprocket side (6305) that seems to require change.  SHould I just do that or do I have to do both? what are your thoughts?

[BobbyR]

Nope. I suggest you do the  job once and forget it. Why would you want one good bearing and one old crappy one? This will be plenty of other things to tinker with on these old bikes.

[old76cr]

You need a 1/8 drill bit and go in about a 1/16 inch to drill out the stake marks. Use a shop vac to suck up the shavings. After that you can try to tap the locking ring counter clockwise to remove. Stick a heavy screwdriver into the axle and force the bottom end of the spacer to one side like Bobby says. This gives you access to the edge of the opposite bearing so you can put a long punch or a screwdriver on it and punch it out. Heat the hub first. The spacer will fall out. Bend the tabs for the spacer back straight that you deformed. Turn the wheel over and knock out the other bearing. There is a sequence to installing the 2  6304 2rs bearings so you don’t pinch the spacer too tight. Lots of posts on this subject. Heat again is your friend. Use the old bearing to tap the new ones into place. You might also have to replace the d ring or o ring on the sprocket assembly if it is loose in the groove so you can pop the assembly back into the Cush hub side.

[kixbox]

This is amazing detail - thanks for that.  It helps a lot - and hope it will help anyone who wants to undertake this daunting task.  I needed to overcome the mental blocks but I think I'm there.  I read BobbyR's instructions as well as yours (and the Hondaman book) all four times to have it mentally sink in.  My plan this afternoon is to take out the the sprocket side, and will get to the hub side if I time permits.

With regards to loclite: should I use the blue one or the red stuff?
 
I intent to re-post progress and pictures. 

[BobR]

Biggest possible snag in the job is possibly removed the carrier bearing retainer. Even after drilling mine out I mauled it badly trying to tap it out. Fortunately I had a spare.  Not saying that will be the case with yours just giving you a "heads up". They make a tool for it but I dont know how effective it it as I never tried it. Bob

[BobbyR]

Do not drive the retainer out by hitting it with a punch screwdriver or anything else. Here is a post on the forum about it.

As I said earlier you can fab up the tool out of a brace sold in hardware stores cheap. It has a lot of holes in it and two of them will line up. In the pic you can see how the screws are attached and used.  No need for brute force.

http://forums.sohc4.net/index.php?topic=74585.0 

[kixbox]

Awesome. 

Now that I am off daddy duties, I’m about to undertake the project. 

I was looking at the wheel studying the steps I’m going to take and have a few clarification questions:

1) sprocket side (pic attached): I see two visible marks only (where I will drill) and four pin wholes on the retainer (CB750K 1978).  Am I correct to presume I need to drill the two marks?

2) hub side (pic attached): it looks like there are four marks the look like they’ve been drilled out before - does it seem as so to you? If so, should I re-drill or assume I just need to turn it?

Thoughts?



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[kixbox]

Okay, feeling fantastic. 

Part 1: Sprocket side (pictures attached):
   - made the tool: 1/8”x1”x36” steel bar ($5.99 @ Home Depot) with a few bolts/nuts 5mm apart to fit
   - with not a lot of force, I gently rocked it left and right and was able to release the sprocket bearing retainer
   - used heat (hair drier for about 10 mins), after that I gently knocked the bearing with a rubber mallet. Few knocks later and it was out!!!

Questions:
    1) is the black rubber inside the retainer an oil seal? How do I get it out?
    2) a small metallic springy ring off from the rubber inside the retainer. Anyone know what this is? I suspect it’s part of the oil seal as I had a faulty one which triggered to start this thread. 

I will update on part 2 Hub side should I get to it tonight. 



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[BobR]

Okay, feeling fantastic. 

Part 1: Sprocket side (pictures attached):
   - made the tool: 1/8”x1”x36” steel bar ($5.99 @ Home Depot) with a few bolts/nuts 5mm apart to fit
   - with not a lot of force, I gently rocked it left and right and was able to release the sprocket bearing retainer
   - used heat (hair drier for about 10 mins), after that I gently knocked the bearing with a rubber mallet. Few knocks later and it was out!!!

Questions:
    1) is the black rubber inside the retainer an oil seal? How do I get it out?
    2) a small metallic springy ring off from the rubber inside the retainer. Anyone know what this is? I suspect it’s part of the oil seal as I had a faulty one which triggered to start this thread. 

I will update on part 2 Hub side should I get to it tonight. 



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 Nice job/ ingenuity making a tool! Yes its a grease seal. The spring is part of the seal and popped off of it.

[kixbox]

Okay, feeling fantastic. 

Part 1: Sprocket side (pictures attached):
   - made the tool: 1/8”x1”x36” steel bar ($5.99 @ Home Depot) with a few bolts/nuts 5mm apart to fit
   - with not a lot of force, I gently rocked it left and right and was able to release the sprocket bearing retainer
   - used heat (hair drier for about 10 mins), after that I gently knocked the bearing with a rubber mallet. Few knocks later and it was out!!!

Questions:
    1) is the black rubber inside the retainer an oil seal? How do I get it out?
    2) a small metallic springy ring off from the rubber inside the retainer. Anyone know what this is? I suspect it’s part of the oil seal as I had a faulty one which triggered to start this thread. 

I will update on part 2 Hub side should I get to it tonight. 



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 Nice job/ ingenuity making a tool! Yes its a grease seal. The spring is part of the seal and popped off of it.

Thanks bud for your input! I ordered the oil seal so should be good to replace when parts arrive.  Working on the hub side, moving along well, will report back with pictures, questions and tips.



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[kixbox]

Part 2: hub side (pictures attached):
   - drilled Mark’s with a 1/8” drill bit approx. 1/16” deep
   - used the same tool (though filed the screwed to make two flat edges (worked like a charm, did not need to apply too much force at all)
   - pushed the spacer to make space, tapped (more like hammered on a screwdriver) and got the right bearing out (success!!! Did not take long, just patience. 
   - spacer with tabs fell out as well
   QUESTION: are the tabs suppose be loose or snug to the spacer (would like to know so I can plan the assembly when all said and done).

... now working on the left bearing and I am stuck.

HELP/TIPS Needed:
I am trying very hard to push the left bearing out but having no success.  It just seems jammed.  What can I do or use to help move this sucker?










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[old76cr]

More heat. Hair dryer probably not enough. If you don’t have a propane torch., get a heat gun, about 35 bucks. Safe and works well. Aluminum expands more than steel.