320/520/521 Inner Bearing Spacer

[mklotz70]

For all the 320/520/521 owners out there, one of the biggest problems out there is that the front inner bearing is nearly impossible to get. I realize boxboy has come up with a source, but I have not seen any indication that there is a ton of them available and since they're from the far east, you can't get them quickly. I've made spacers before and I thought about posting this info in that thread, but figured a new one would be a bit clearer. The old style I did had a lip that dropped over the "boss" at the base of the spindle and required a larger hole in the backing plate to work. Not good if you're running stock drums. I was chatting with Wayno(owner of my old NL) and he started talking about a pre-made washer....yada, yada.....it took me about 10 min to finally pull my head out and understand what he was saying. These spacers are the result of his idea...Thank you Wayne!! :)

 

For the guys running Beebani's disc brake kit, this will finally allow you to put new bearings in your stock hubs. :)

 

To use these spacers you will need to remove the stock spacer on the spindle with a pipe wrench, heat or chisel.

 

 

Okay...the pics help to show how the two spindles and bearings are different so that everyone will understand how the spacer works. The spindle on the left is the 521 spindle(dimensionally the same as 320/520) and the one on the right is the 620. Notice the difference in the height of the boss at the base of the spindle.

 

 

 

The net result is that the bearing cup is still at the exact same height on both spindles. The 620(drum rigs only) bearing has the seal shelf built onto the backside. It's about 2mm shorter then the 521 bearing and it's spacer, but the 620 spindle boss makes up for it. The 620 bearing is on the right. You can see the difference.

 

 

 

 

 

If you try to put the 620 bearing straight onto the 521 spindle (after removing the stock spacer), you can see that it's too short. This is brings the drum inboard enough that it will rub/grind on the shoes. The second pic here is the 620 bearing on the 521 spindle.

 

 

 

 

 

I posted the "how I made the spacers and dies" part of this spacer build in the "Let's see some machine work thread"... 

https://ratsun.net/topic/8292-lets-see-some-machine-work/page/15/#comment-453852

 

In this thread, I'll just show the spacers. They're nearly a perfect thickness. I think they push the bearing/hub out a few thousandths, which shouldn't be a problem at all. On old drums/shoes that have seated in, you might get a bit of rubbing on the edge of the shoe for a few stops. With new parts, it won't even be noticed.

 

 

 

 

 

The end result is that the 620 drum bearing is back at the correct height as was the original stock 521 bearing. :)

 

 

 

Both bearings say 32KB02 on them, but the 620 version has a "/11B" added on the end. You will not find a correct listing for the inner bearing if you are looking it up under the 320/520/521. Trust me, the parts manuals are wrong! PM boxboy if you want a new stock inner bearing.

 

**edit 5/2/22**

 

They're getting a bit harder to find for the 620, but it looks like these numbers are still good:

32KB02/11B (typically Koyo, I think)

Beck/Arnley 0513178

SKF BR31

National A24

The dimensions you are looking for are 32mm ID, 65mm OD and 27.3mm wide.  I had Timken Set 24 listed here, but I just looked them up again and they're not correct.  The Beck/Arnley number seemed to come up the most on ebay.  I've never had an issue with the parts stores when asking about 620 drum inner bearings, but then again, I never had much reason to ask. 

 

I don't think I had a good pic of the backside of the 620 bearing.

 

Edited May 2, 2022 by mklotz70

[datson4life]

"After removing stock spacer"

What do u mean by that?

 

Also to take out inner bearing i had to remove the seal , are those still available? And a ring came out of bearing location aswell

 

Whats the purpose of that ring?

[mklotz70]

You're right....it's not that clear in this thread.  Here's a vid on taking the stock spacer off.  You can see it in above pics, I should have showed with the bearings removed.

 

 

The spacer came from under the seal and on top of the bearing race.  You can put it back in if you want.  It's just to make sure the seal doesn't get seated in too far. 

 

New seals should still be available....

 

TIMKEN 1977

SKF 550225

 

This will give you an idea of how the spacer works

 

 

 

 

Edited February 27, 2022 by mklotz70

[datson4life]

Perfect! Thanks Mike