Talked with Greg at Piston Bikes seems like a nice fellow and answered a ton of questions I had. However....I want to know if any of you have read, seen, used this GT5 configuration. Another question I had is I just helped my buddy install a Arrow GT5 into his bike tonight and the gears in the clutch housing are different from his Ebay style motor. The Ebay motors gears are just straight toothed and the GT5 gears are helical (slanted). Is this a performance advantage or is the advantage having gears that produce less noise? One last thing. I asked Greg if there was anything else that I needed to add before I installed this kit and we talked about an expansion pipe which he thought should be added later but he highly suggested the High Performance Round 66cc Head to add right away. Does this increase HP at all or is the effect of added HP from a cooler motor? Should I wait and just get the Cylinder and head from CR Machine at a later date like the beginning of spring? This is the head from Piston Bikes (Made by CR) http://www.pistonbikes.com/Grubee-Skyhawk-Bicycle-Motor-p/1gru66phaf.htm This is the Cylinder and head directly from CR. http://www.shop.crmachine.com/Stage-1-GT-5-Top-End-Kit-66cc-BTKS1.htm If it helps to know Im 165 Lbs and live at over 5000 ft elevation so while being light is beneficial my elevation robs the horsepower. Thank you for any replys, Dan.