If you don't have a 'tech'...you hv NO idea what you have. If the valve springs are weak, you could be floating the valves and loosing power. What is your gear ratio(?) Maybe it's on 'nose-bleed' at 35-40mph!! Many un-knowns involved. JMONo tach, engine just gives up pull around 35-40mph @ max RPM. I'm trying to stay away from gear changes to keep a good bottom end on it. Currently running all the normal BSP parts, weinie pipe, filter adapter, re-jet, BSP-2 cam.