Sorry dude I'm getting old. I really don't give a shit if you can go over 70mph or not, but since some times we try to help out the retards, I posted in your thread. If you have a ported 4 mill with those crap boyeson cages with the little tiny built in aluminum reed stuffer deals then they are probably choking your motor a bit. Kinda like what Fouldout421 had mentioned in the shout about how he ran them on a bone stock motor but wouldn't on anything more. You said you thought something was holding your motor back, before you figured out how to count and saw that you only had a 12 tooth sprocket on the front. I would think lack of airflow on a ported motor could be a contributing factor? I could be wrong. You prob know more about it than I do. If you don't want to spend them money on parts to make your turd run better more power to ya. I really could care less. Now go out your helmet back on and enjoy your jello.