ORIGINAL: radioactiver/c

Hard to buy a 5 hp (so called mid mod these days) most engine builders do full mod for about $600 , this yeilds 5.8-6.2 hp. Beware of outrageous claims of hp levels of more than that.The factory cylinder casting does not have enough material around transfer ports to suport that power level.

to be breif and keeping this complex topic simple
Set your squish to .018"
stay on the conservitive side with intake and exhaust timing, shoot for 146-148 on intake and 176-178 on exhaust
widening ports without increasing timing will increase power also but don't go too far,stay under 15/16 max width
combined widening and increasing timing will make morepower and increase rpm
swap stock carb to WT257