Some vehicles run better with 87 or 89 octane gas than they do with 93 octane, it is the same for the 650? I put 93 octane in the last time I filled up, and noticed that at top speed the engine seemed to want to rpm down a little bit then it would come right back to normal (matter of seconds). Would this be the cause of it or what?[img]i/expressions/face-icon-small-smile.gif[/img]

 

Generally if you dont hear any spark knock, or pre ignition, then you dont need higher octane gas. Simply put, it burns slower, reducing pre ignition. Most Carb engines dont seem to care. I plan on plumbing in an in line filter on my quad to help keep it even cleaner.
In other words, IMHO run the cheap gas with a good fuel filter and you should be fine.