I have sorted out the parts for my back suspension and figured the information maybe useful to others.
The equivalents for the following Yamaha bearings and seal are:

93317-31701 drawn cup needle roller bearing, size 17mm x 24mm x 20mm NTN HMK1720C
93317-21746 drawn cup needle roller bearing, size 17mm x 24mm x 15mm NTN KH1715
93320-32403 drawn cup needle roller bearing, size 24mm x 31mm x 28mm IKO TA2428Z
93109-17048 single lip oil seal, size 17mm x 24mm x 4mm (common oil seal)
93399-99919 special bearing, no equivalent found (have to buy the Yamaha part)

Posts like this are really useful but they just get buried and lost. I made a web page and I hope others will contribute to it.
http://litetek.co/Guide_Suspension_Bearings.html
cheers
Blair

See here;

http://www.fzrarchives.com/ipb/index.ph ... =60270&hl=

Includes cheap replacement special bearing.

Thanks Mr Willandrip.
Seems like there is already a conflict on the 93399-99919 size. Have to expect that.
cheers

The HK1720C, Yamaha Part No 93317-31701, is incorrect. That bearing is 17 x 23 x 20
You need an IKO TA1720Z or NTN HMK1720C which are 17 x 24 x 20
cheers
Blair