Really good info Tex. It does light throttle just fine threw all the gears. I don't know the ratio of 6th but it did seem to bog a bit in 6th. As far as the head I don't know if it was ever cut. We did use a machinist stone to make sure the face was even but that shouldn't have taken much off.
As far as tuning this would be my first go round. I thought about soaking the carb in seafoam because the throttle was sticking a little. Also I never checked to see what jets were in it so this would be a good time to check. Also there is a fuel filter in line. I can replace that or should I just lose it all together?
As for how it was acting it would lose all power almost like if I had pulled the plug wire. I would let it and it was just fine part throttle. Even up over half throttle opening up the powervalve its good just when I give it the full load.