My bike use to bog on this one hill i ride everyday in fifth gear (shifter kit), sometimes i would barely make it up with out downshifting... Now goes right up the same hill without any drop in rpm in the same gear.
The Jet silver motor I bought and installed on another bike pulls right up this steep hill (not the same hill as previously mentioned) with a 44t sprocket. Before I modded my bgf (ie. it was in new stock condition), I had to pedal assist the bike up this same steep hill with a 44t sprocket.
Obviously the new head made a difference for me on my BGF motor and in the PK 80 motor that you saw on ebay (i bought my Jet silver from the same people)
Thread on fitting slant head to non slant head motor:http://motorbicycling.com/f13/new-sl...oost-6621.html
SOLD..50cc Morini S6-T 5.8hp,
44 tooth sprocket, Early 1990's Diamondback Frame, 26" WTB FX28 Wheels w/ Shimano XT Hubs,
Dellorto PHBG Race Edition 19mm Carburetor, 4 Valve Reed Intake (combined adds ~2hp),
Homemade Expansion Chamber, Homemade Steel Pack Muffler, Homemade 1.6 gallon Rear Gas Tanks
TOP SPEED: 54.0 MPH (not gps tested yet)