The clutch is off a tractor of some sort or a go kart mabe i have replaced the clutch because there where 3 missing teeth.And about to change the engine to a 6.5hp which should go faster.Its geared at 1 to 7.
yes 7:1 but is gonna go quite slow i may gear it slightly higher 5:1 or 4:1.
with 4:1 it'll take a while to get up to top speed i say 6:1 gear ratio nice mix of speed and torque

with 4:1 it'll take a while to get up to top speed i say 6:1 gear ratio nice mix of speed and torque
I have a 3.5hp with 8:1 and it's got piss poor acceleration. Top speed around 25mph.
well 3.5 are too small for any real fun, and what size tires are you running?
edit- ahha i didn't realize this was a 3 hp engine yea, 4:1 is a little ambitious for a little engine.