Well, I tried.
To be sure of what you have you need to look down on the drivers side just in front of the side cover and it should be stamped exactly what you have.
And you're sure the 10w-40 isn't for the rear-end lube? The fill hole is about by the lower shock mount and drain plug(10mm) is underneath.
If it really sounds like it revving at all it can make and you're sure the throttle is opening up all the way, you may want to look at the belt and see if it's worn to thin.Before you take the belt off, thios would be a good time to inspect your clutch operation, should go to the top of the pulley when revved, on the centerstand.
Other than that, check compression,check plug, fresh fuel filter,clean air filter.