Topic: 78 CB750F Front Bearing issue

[pmurph1x]

I am trying to get a '78 CB750F3 back on the road. I'm almost there.
This week I decided to change the front wheel bearings as I had the wheels off for new tyres. The original bearings rotated freely and seemed OK but they were probably the 35 yrs old.

Anyway I got the kit from All Balls. Got the old bearings out with some persuasion. Put the new ones in the freezer overnight and tapped them in with the old bearings - only tapping the edge until I heard that ringing sound of them being fully seated.

However before even installing the axle I tried to rotate them with my finger - they were very tight. It looks like the spacer is pushing on the inner race on both sides. I put the axle assembly in and installed the wheel. - It is way too tight. I havent even put in the brakes and the wheel wont rotate easily.

Has anyone had this issue before? It seems like I got the bearings too tight against the spacer but the only way to avoid this is to not seat them all the way.

Do I just need to take it for a ride to see if they will settle in?

Thanks Paul

[flybox1]

Positive they seated all the way? If you didn't, your axle stack, when tightened down will bind both bearings.
Please remove your axle and bearing retainer, and post up a closeup picture of each bearing.

[pmurph1x]

Positive they seated all the way? If you didn't, your axle stack, when tightened down will bind both bearings.
Please remove your axle and bearing retainer, and post up a closeup picture of each bearing.

Thanks Flybox. Ill get a pic later - got a
bit sidetracked tonight. However I think that the bearings
are binding because the inner races of the left and right
bearings are jammed up against the spacer. Could this be possible?
The spacer is real tight and has no movement whatsoever. I noticed this
Even before I put the axle in.
   In fact initially the axel wouldn't go in easily because
the spacer was slightly off center. I had to use a drift and hammer
to gently persuade it to move to the center so that I could get the axle in.

[pmurph1x]

Heres the right side bearing with the retainer removed:


Here's the left (speedo) side bearing:



Even with the axle out they are really tight. Hard to see in the pics but the spacer is jammed against both inner races. Have I tapped them in too far?

Any ideas are welcome. Thanks.

[Bodi]

The bearings should spin freely with the axle nut loose and with it tight.
The bearing system locates the wheel on the axle via the retained bearing. The other bearing "floats": it should be able to move in its bore to find the spot where the balls in both bearings are riding in the centres of their races.
You have pushed the floating bearing in too far.
You can easily correct the problem though. You have to gently tap on the inner race of the retained bearing. I just use the axle, inserted from the retained side with no external spacers. Using it like a slide hammer works well. Not super heavy strokes though! You can damage the balls or races by hammering on the middle race, but unless the floating bearing is way too tight in its bore the force needed won't damage the bearing.
This will leave both bearings properly aligned when the axle is tightened, since you are pushing them both the same way. With the axle nut loose, the spacer should be a bit loose when properly set up.
By pushing the floating bearing hard against the spacer, you made the bearings misaligned in opposite directions.

[pmurph1x]

Thanks Bodi. Had to read it a few times to understand but I think I have it now. Ill give it a shot this afternoon and let you know. It makes sense though. Thankfully I didn't try going for a ride, if I understand your post fully that would really have buggered them up.

[pmurph1x]

I tried Bodis suggestion but it didnt help - bearings are still tight. At this stage I think I'll call the bearings the winner in this fight and take the wheel to the shop tomorrow. Flybox and Bodi - thanks for your responses. Next time I'll remember not to seat the floating bearing all the way.
Paul

[flybox1]

you might still be able to salvage it.  insert a punch from one side, and working around the inner race of the bearing on the opposite side, tap, tap, tap.
you only need a fraction of a mm and the inner spacer will rotate freely.
if you've decided to take it to a shop and pay ridiculous shop rates, then just whack the inner spacer to the side(bending one of the tangs) and knock out the bearings you have in there(probably ruining them), and order another set.
although its cheaper to find a local bearing supplier and buy through them  just take in the bearings you knock out. they'll measure them.

[pmurph1x]

you might still be able to salvage it.  insert a punch from one side, and working around the inner race of the bearing on the opposite side, tap, tap, tap.
you only need a fraction of a mm and the inner spacer will rotate freely.
if you've decided to take it to a shop and pay ridiculous shop rates, then just whack the inner spacer to the side(bending one of the tangs) and knock out the bearings you have in there(probably ruining them), and order another set.
although its cheaper to find a local bearing supplier and buy through them  just take in the bearings you knock out. they'll measure them.

I actually tried that but I cant get the bearing to move at all. I'm using a 1/2 inch bar and I sharpen the edge every so often to try to get a grip  on the champfer between the bearing and the spacer but as there is no gap between the spacer and the bearing it just keeps slipping out when i tap it.
Also you mentioned "spacer tabs" There are none on this bike. I guess they went with a different setup on the comstar wheel.
I might call around and see if I can find another bearing and give it another shot tonight. Thanks for your input.

[flybox1]

check the last 2 pictures in this thread..  did your bearing retainer look like this?
http://forums.sohc4.net/index.php?topic=10550.0

[pmurph1x]

check the last 2 pictures in this thread..  did your bearing retainer look like this?
http://forums.sohc4.net/index.php?topic=10550.0

I think you meant "did your bearing spacer look like this?"

No it doesnt have the tabs like that one. It is basically just a tube with a small inner chamfer on both ends. This is my first 750 but I'm guessing the tabs on the one in your link help keep the spacer in place while you are installing the bearings and axle. In my bike the center of the hub provides a snug fit for the spacer meaning it doesnt flop around while you are installing the bearings. Here is the drawing - Item 4 is the spacer.


I stopped at the bike shop and they will charge $15 to put in bearings - not bad. However I'm not convinced they wont have the same issue but at least theyll have the proper tools to get the bearing out if needed

[pmurph1x]

OK so there is something really messed up here. Since I last posted I took the wheel into the shop to have them put new bearings in the front. When I went in to pick it up they said that the bearings were fine but the spacer was too long so they ground it down a bit. I was a bit irritated as it worked fine for the last 35 years and 36K miles. Anyway that’s a separate issue – I think. The speedo side bearing is still binding so I have a new all balls set and a new spacer on order. This time I’ll fully seat the retainer side first and then partially set the speedo bearing and let the speedo housing do the final positioning.

I now have another issue which I don’t think is related. My wheel seems to have moved so far to the right of the bike that the brake disk is almost rubbing the right lower fork and is actually rubbing the side of the slot on the caliper holder.

I've been scratching my head for the past few days trying to figure this out. The only way I think this can happen is:

1. The guys in the bearing shop accidentally put in a shorter spacer on the Right (retainer) side. The spacer is 23mm long.
or
2. The spacer is actually pushing the inner race of the bearing into the wheel hub - seems unlikely?

Does anyone have any ideas what I can check to figure this out?
How long should the right side spacer be? - length is not mentioned in the fiche.

Below are some pics that will hopefully explain a little better. I'm itching to get this bike on the road and I have a Highway patrol inspection coming up on Aug 7th so I hope I can get it figured out in time. Thanks for all the help so far with this bike.

[pmurph1x]

Problem solved. I put the axle in ass backwards even though I had the fiche printout right in front of me. Stupid mistake - so obvious looking back.
CHP inspection is next week so I hope I can pass that. I have a bit of a dent on the front rim to be taken care of but hopefully they will let that slide, it doesn't look like I'll have a replacement wheel on time.