'03 Vinson low top speed

I just rebuilt the carb (Moose kit) on my '03 Vinson Auto. It previously was running super rich and I had trouble getting it to start and idle. Now it runs pretty good in those areas.

My problem is that it does not run very fast on top end. On a paved road I can barely get it to 30MPH in high range. It carburates cleanly all the way and never does anything weird. I am certain that a 500 should go faster than this! I checked the throttle and it is all the way open both at the handlebar and at the carb. Any ideas? My battery needs to be replaced as I have to jump it, but other than that all is good.