Hi All, I’m about to rebuild a gearbox and am confused as to whether the Single and double roller bearings can be reused or if it is best practice to replace. Some of the guides I’ve read say “be careful removing because they are very expensive” - what does it matter if you have to replace it anyway?
If you can reuse it, what do you look for?

If you are talking about the mainshaft and 1st motion shaft ball bearings, if they feel at all rough or loose when spun by hand, replace them.
Ditto if the plastic cage in them is at all damaged. They get brittle with age and dirty oil.
They are expensive but not outrageous. Buy RHP if possible. Not cheapo replacements.
Re the needle bearings, always replace.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Ditto for drmini.
Many How-To instructions seem to be happy reusing bearings. Some businesses sell used bearings but it is a lot of effort to get the box apart so seems best to replace as many wearing parts as possible while you are in there.
Double row is $86 and single row is $70 (4 synchro) or $156 (3 synchro) for RHP brand.

Yes ironically the ones that are considered reusable are the ones that you can still buy in good brand (RHP). The ones we definitely don't want to reuse (the needle bearings) are unfortunately the ones that often come in crappy no name Chinese made.

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Build thread for Supercharged 1275 1967 Deluxe Resto
Build thread for Mini ute conversion 998cc Turbo

What are the best brand needle bearing to use in the box.

INA (Germany) or Torrington (USA) used to be two of the best needle bearings years ago, but are hard to find now.
Next time I go to my local bearing shop I will take Chinese samples and enquire.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

If you get any leads, let us all know Doc

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Build thread for Supercharged 1275 1967 Deluxe Resto
Build thread for Mini ute conversion 998cc Turbo

https://www.koyo.eu/en/news/289-koyo-ko ... ation.html

Torrington is now Koyo.
CBC bearings is an INA distributor.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

If it is any help to anyone: for my recent 4 synchro rebuild, I was able to order Torrington idler gear bearings.
For the layshaft (22G1040 gear) I had some old stock SKF bearings:
CHM141 is the larger needle bearing (2 required) - SKF number was K20 X 26 X 17 -2-4.
HYL8473 is the 1 smaller needle bearing - SKF number was K14 X 18 X 17 -2-4.

Don't know whether SKF still stock these, though.

Bill that last one isn't right, the small bearing is K16 x 21 X 17 long.
It's the mainshaft nose bearing that's 14 X 18 dia.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

That makes sense - mainshaft was 14mm for early all synchros. Copied the numbers from the original SKF boxes onto my parts list and may have mixed the contents into the wrong box.
Thanks for pointing that out. At least it is impossible to fit the bearings wrong-way around in the gearbox.