Without question, the best combination for the vast majority of riding is the BT45 pair from Bridgestone.  Improving on the very good BT35's, these too perform extremely well on lightweight sporting bikes like the CB-1.  The price should even be reasonable, giving no real reason to look elsewhere.

Full-out ultra-sports riders who stick the bike in the back of a truck to take to the twisties in good weather will no doubt rejoice that there's a Michelin Hi-Sport combination that can be squeezed onto the bike, and radial bigots can try the Metzeler ME-Z1/ME-Z2 in non-stock sizes, but the BT45's are such an obvious superb match to this bike.
 

An interesting choice might be the Avon radials, AV27 front and AV281 rear.  I am not yet recommending them, partly because the AV281 is not readily available in the USA.  Also, the BT45's are a very good tire, and it's not yet clear to me that these radials offer enough of an advantage.

Unfortunately the mail-order prices for the older Bridgestone BT35's have recently increased, which prices them out of the budget market for this bike.  A second strike is that the Michelin Macadam 50, which conversely has lowered in price, isn't available for the rear as their fitment guide suggests.  That leaves the IRC Carapace RS-320, a budget sport-touring tyre that will work well enough if you're strapped for cash.  If you're a bit nervous about traction, you can use the IRC rear with a BT35 front, but that would cost more.

I'd definitely go for the Bridgestones.

Avon

Bridgestone

Continental

Dunlop

IRC

Metzeler

Michelin

Pirelli

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