I wanna say it's an 8.9ish % gearing increase, maybe less, but it starts with 8,,
It's really nice. It's a lot more relaxed at open road speeds.
It's still got fun acceleration. The only downside I've seen is in town where the limit is low. Instead of shifting up and just rolling along I worry about lugging it, and I have marked the speedometer with a China marker with the shift points and MPH .
IF your speedometer was accurate before the pulley swap then indicated 60 MPH will now be so close to 65 that nobody will know.

Thanks for that Dave and JOG2-Dave we still do it the proper way in the U.K. good old mph none of this dodgy kph, the europeans only invented kph so it sounds like they're going faster than us  

I don't know for sure the entire list of models/years.  The EN454 from 85-90 works.....and the Vulcan 500....... but I don't know what years.

But it is not a "bolt on" deal. without some work on a lathe or milling machine.  The pulley has to be machined thinner where the shaft slides through - and the splines are hardened and pretty tough on the carbide cutting tools (frequent sharpening).