I have been running the Honda HP4S synthetic oil in mine for quite some time now, with no problems. Just be sure it is the red bottle, not the grey bottle since the grey bottle has moly in it, which will fry a wet clutch. To elaborate, I had a shift fork bend from a stick hitting my shifter so the engine was completely torn down. The guy working on it said everything looked almost new, in an engine with easily 500 hours on it.
08 700xx,HMF Ballance Exhaust,HMF Optimizer,Honda Racing Skids, J&J A-Arm Skid Plates, Grip Heaters,13 Tooth Sprocket,Prm Six Pack Rack,6000k Hi/Lo HID lights,22x9-11 Kenda Kutters- summer,24x10-11 GBC Gators- winter,Trail Tech Voyager, Powermadd Handgaurds, Front Springs on All 4 Corners, GBC X-Rex 23x7-10, UNI Air Filter, Custom Outerwears Pre-Filter for a UNI,Odi Rouge Grips,Reverse Rev Limiter on a Switch,L8ton 11/16 Sway Bar