I use my 421 cub for drag, trails and mostly hill climbs, I have 19cc domes, 35pwk, 152 main, 48 pilot and needle on the 4th clip. It's has the aggressive port job from HJR and a lock out clutch on a modified stock tranny. +7 on timming and burning 110 octane. I made 96 hp on redlines dyno. I have had zero problems running on the trails. I run a 12 front sprocket and a 43 rear and 22.11.8 10 paddles. It had good wheel spin when I need it in the soft and steep hill climbs and enough gear without winding out in the drags.