Where did you get your plugs from? I just ordered some off ebay thinking hey they're cheaper online. Then as I was browsing online ran across articles about "fake plugs." So be warned now! On the back of the box NGK CR9EIX iridium spark plugs it should read "M10" some of the counterfeit NGK read...
Not sure if this relates to a similar issue we had with a Harley, however would be simple to check. The clutch switch housing could possibly be bad or stuck and need some a cleaning. Maybe? Maybe not. Good luck to you though!