You know, that search function works wonders... 
Among the numerous threads that pop up when you search for "synthetic" is this one: http://www.suzuki-bikes.com/forum/showthread.php?t=6793
Mobile 1 & Castrol seem to be popular choices - I use Castrol in my cage, but will be using Mobile 1 in the C50.
In that thread we also learn to avoid the high mileage/environmental synthetics containing molybdenum (sp?) that can cause clutch slippage in wet clutch bikes.
Among the numerous threads that pop up when you search for "synthetic" is this one: http://www.suzuki-bikes.com/forum/showthread.php?t=6793
Mobile 1 & Castrol seem to be popular choices - I use Castrol in my cage, but will be using Mobile 1 in the C50.
In that thread we also learn to avoid the high mileage/environmental synthetics containing molybdenum (sp?) that can cause clutch slippage in wet clutch bikes.