most clutch for mini bike has 12 tooth front gear. My motor builder suggested using a 14 or 15 tooth to slow done how quick it would take off but it will add speed at top any issues with this with a 8 to 10 hp 2 stroke? Trying to slow down take off.
I would keep the 12 tooth clutch & go with a 60t rear sprocket, if you can get one.
That would give you a ratio of 5 - 1, & allow you to shorten the chain, which is always good.
A 14t clutch & 72 sprocket gives a ratio of 5.143 - 1
A15t clutch & 72t sprocket gives a ratio of 4.8 - 1
Either way, with the HP of that engine,, I would think those ratios would be more than fine, & tame the take off.
If running a Max torque clutch, I would run a green spring, if you haven't already.
That spring will help smooth things out a lot also.