Can anyone recommend a good O ring set, for multi purpose uses on the CBR?

For example, to replace carb drain screw O rings, amongst others.

Or will any set I can pick up from flea bay, Amazon etc do?

In my experience (and opinion), you're better off buying just the O-rings you need, rather than a set.
The sets look to be good value, but they tend to be low quality items (unless you pay a lot), and you always end up with loads you'll never need/use.

I've used this site several times . . .
http://simplybearings.co.uk/shop/index. ... =4501_4705
They're good for Bearings too.

You'll need to be able to accurately measure the O-ring(s) you need (or the space/part it's going in/on/around), a decent enough Digital Vernier Caliper can be got for around a Fiver, and will be useful for plenty of other jobs too . . .
http://www.ebay.co.uk/itm/150mm-6-Inch- ... 2c86689e41

You also need to be aware of the material the O rings are made of, some will not stand up to petrol.

Yes, my bad, should have linked to the Viton O-Rings . . .
http://simplybearings.co.uk/shop/index. ... th=19_4462

Maybe not what you are looking for but if you need full carb kits at some time.
viewtopic.php?f=64&t=42551
cheers
Blair