Only, if for some unknown reason, your engine pings, would you need a higher grade gas. Most cars/bikes that the mfg recommends higher octane gas can use regular. Every magazine and newspaper that I've read where comeone wrote in asking that question, the answer has been the same....yes you can use regular instead of premium. If you have a high perforence car/bike you will more than likely need premium.
I have never had a vehicle that required premium, even my 2 Vettes ran exclusively on regular...unless I was going to a drag or ralley for which I wanted all the power I can get. My Harley's manual recommended premium, but I only put in regular for the 9 years I owned it and never had a problem.
I read once that if the mfg recommends premium .... you can use regular, if the mfg requires premium.....then you have to use premium.