Re: mph issue
I've found on my bikes that the 'surging' is from the engine being very close to being the right mixture but a little too much on the rich side. it feels like the bike is bogging & then it will get a little 'crisp' burst of speed, then go back to bogging... re-jetting a little smaller has always fixed it.
This is also how I know when I have the jetting right, it will run real crisp & clean with just a small bit of 4-stroking. (the little bit of 4-stroking tells me that it's not too lean!!)