Need to figure out where I can get bearings and oil seal for my 1969 DT1B. Numbers 9 and 10 on this diagram. Also spacers 35 if possible, otherwise I can Emory down the rust on mine. Thanks!

On discontinued bearing and seals i just take them to my local Industries store that sells all types of bearings and they match them up. Always seam to have what i need. May take a day or 2 to get them in if they have to order. 
 

I have the seals . . . so many that everyone is welcome to buy them at just $3.75 each + 1.95 (for US shipping) 
I probably have the bearing as well . . . can you give me any numbers found stamped into the edge ?

If i'm reading the middle part of the number right it uses two 6202 bearing double sealed & one 6204 double sealed in the sprocket carrier. That's the early wheel with square swinging arm QD wheel & good system it was too. #9 & #32

www.partzilla.com/catalog/yamaha/motorcy...1969/dt1b/rear-wheel

Bearing part no: 90387-20157-00
seal part no:  93104-4420-00
Collar part no:  90387-20157-00

would need 2 bearings, 1 seal and 2 collars if you have them. 
Thanks

I simply get whatever part number I need from the various sites that show exploded views and then search Ebay with something like "Yamaha (part number)" . You'll find various sellers will usually be out there and you can choose based on price, delivery time, etc...  I've restored a handful of enduros and rarely get skunked searching Ebay that way. I stick with OEM Yamaha parts.

While I agree that if I get OEM parts I should get OEM quality, I do believe that a 6202 bearing is a 6202 bearing, and should fit. The quality issue then comes up, and that is where going to a bearing supply house can be a huge bonus, as the counterman should be able to assist once he knows your application. Yamaha would have sourced and used bearings of a specific quality that was specified by engineering.

I believe that any bearing also has some additional lettering (maybe) to indicate tolerances of the bearing (yes?).

Bearing factors.  If RTs memory is holding up, you need:

Koyo 6202 2RS C3 x 2.

Koyo 6204 2RS C3 x 1.

Take seal with you. The size is on the seal and unless it is a special regarding thickness, a good bearing stockist will have them in stock.

Better quality than OEM ( because penny pinching yamaha accountants usually tell production to fit Koyo 1RS bearings) and all at a fraction of the cost of buying them in yamaha boxes.

Good info except I don't ever recall a wheel bearing spec'd with the C3 clearance? Cn clearance (aka "normal clearance", which is usually not marked on the bearing) is what I recall for wheel bearings.

C3 for crank bearings? Yes. Just not wheel bearing. Could be wrong though?

2RS is a definite yes even if not originally spec'd... means a seal on each side of the bearing.

I'm also not sure it was "penny pinching" to specify a bearing with one seal or shield... most original wheel bearings have the open side placed where it is possible to wash the old grease out and repack with fresh grease without removing the bearing.

This is important because if you strictly follow ball bearing handling procedures, you NEVER hammer on the inner race and if you do, you replace the bearing. It's impossible to remove most Yamaha wheel bearings without hammering on the inner race so if a Yamaha Enduro wheel bearing is removed "technically" the bearing should be replaced... and new one installed only by tapping on outer race.

(In practice, most people that clean and pack with new grease remove the bearing and reinstall after... even though replacement is recommended if inner race was hammered on.)

In my experience, all manufacturers fitting 1RS bearings fitted them with the exposed side to the inside of the hub. Water gets past the dust seals, down the spindle and gets held inside the hub. Bearings rust from inside.

Never came across one fitted the other way from the factory.