elite 80 4 stroke help

[mopar4u]

I'm 220lbs and have this engine in my spree chasis. I put new Honda 10g rollers in it. I removed the grease cover on the drive clutch and am running the drive clutch dry. The belt measured right at nominal width according to the manual. I can only hit 35mph on flat road. From what i've read I should be able to get to 40 - 45mph. Air filter seemed clean. Rear tire is stock size. Any ideas?