I remember years ago when this bike was sold as the Suzuki Savage (sic)....
A 30hp air cooled single...you're probably close to or at full throttle a lot of the time, I'd probably try Rotella T4 15W-40 or one of the Valvoline motorcycle oils first to see how the bike likes it. If you're not too picky about JASO MA/MA2 (I'm not), VR1 would be a very good choice.
If you don't mind spending $15/qt, go Red Line and call it a day. At the very least you could likely extend your oil change intervals.