You should run better than that...I'm running a stock stroke, stock cylinder drag ported 350 and weigh almost 300 lbs and turning upper 7's in the 1/8th. My 150 lb friend got a 7.52 on my bike, and could easily break into the 7.4's, maybe 7.3's with better launches. Not saying your times are bad, you just definitely have room for improvement. I noticed the biggest difference when I changed the gearing.
I know you said it was an 1/8th mile track but the length can be different depending on where you go. My track is 660 ft, where some 1/8th miles are only 600 ft. That 60 ft will make a noticeable difference in your time. I think the track race-a-holic was at is 600 ft, it seemed shorter than my local track :shrug: :beer: