The building of the CB350 is progressing well. Wallet is rapidly emptying (thank God for Kevin's $900.00 handout!) I'm about to order set of tyres - what are we using on these little bikes??
I use Dunlop TT900s with GP compound, relatively inexpensive although supply can be spasmodic...it's not unknown for racers to fly tyres out from the UK, particularly for Dunlop KRs and Avons, without paying much more than across-the-counter here. My bike has 90/90 front and a 100/90 rear, you can go bigger but risk overtyring the bike and exposing the inadequacies of the chassis when it gets busy (turn 3 at The Island !). It'll be interesting to hear from our compadres regarding their viewpoints on tyres, but get the best you can afford. If you are riding a lot you will get a season from a front, but may need two rears.
Mandy Beales uses Avon AM20 90/90x18 on WM2 rim on the front and AM22 110/80x18 on WM3 rim on the rear. Grip is very good and tyre wear is greater on the front. We have found to retain best results we replace both front and rear after a maximum of 5 meetings but usually 4. Obviously we try to run with fresher tyres at major meetings. Remember tyres can be cheap insurance.