Rear wheel bearings

I'm intending to replace the bearings in the rear wheel of my '74 850. According to the books, thee are two single row bearings in the hub and one double row in the brake drum. I want to use sealed bearings for all 3 if possible, but I can't find a sealed version of the 17 X 40 X 16 mm double row. It seems that the standard (ISO) bearing is 17.46mm wide in sealed version. Is there a sealed bearing of correct size, or do you have to modify a spacer or something to fit the larger one?

Thanks

Hi Maylar
I have looked in the skf book.
The code for a 17 id 40 od 16 wide standard unit is 4203 atn9
CNW website shows a sealed unit.....machining required!!!!
The code is 5203 a 2rs1tnp.....I bet it is bigger outside diameter.
Stu

maylar said:

It seems that the standard (ISO) bearing is 17.46mm wide in sealed version. Is there a sealed bearing of correct size, or do you have to modify a spacer or something to fit the larger one?

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I think you will find that Walridge Motors sell the correct size sealed bearings.

http://www.walridge.com/section/view/

The Walridge part number for this bearing is apparently: 06-7688/S but maybe check first before ordering?

I haven't talked to Mike Partridge about the sealed bearings he sells, but I have never been able to find 17X40X16 mm sealed bearings in the proper load capacity.

The common modification requires the bore in the rear drum to be machined an additional .055" and the dummy axle turned down .056" to accomodate the commonly available 17X40X17 sealed bearing.

The same bearing is used in the front disc brake wheel. To use the 17X40X17 sealed double row you only need to shorten the spacer by .056".

I have never had an issue with the nonsealed double row, so have never done the modification for the rear drum. I do use them in the front, however, since it's easy to find someone to cut the spacer, or buy one from Old Britts for about $30.

I got the double row sealed bearing from Mike at Walridge. He assured me it was what they sell at Norvil for a correct replacement part.

Dave
69S

I got the double row sealed bearing from Mike at Walridge.

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Is there a an OEM mark on the bearing like 4203 2RS? or 4203 atn9 2RS?

I don't know. They are in the wheels now but not on the bike yet. If I can get to one or the other without taking the bearing out I'll check.

Dave

It says 4203RS

Dave

I did the modification for the double row bearing about 15 years ago. It seemed like a good idea. I don't think it's really necessary though. Just as a funny story; after I did all this stuff to the rear wheel I was coming back from Alaska and all the teeth on my rear sprocket basically disappeared. Just out of Fort Nelson, BC. They were there at my lunch stop and two hours later they were just bumps. Long story, short; couldn't order a new drum because it wouldn't fit, spent 5 days there getting a new sprocket and having it welded on. Fabulous people, actually one of the highlights of the trip. Great machinist. I put a stock one back on when I got home.