You will need bigger carbs for air craft use if you want any kind of performance. You can overcarb a car but you will still get alot of performance from it and as long as you can ignite and burn the fuel well you would have gain some reliablity also. Cars don't deel with rapid changes in altitude and fast g forces like an aircraft and this is why a bigger carb with better pumps on them work well on aircraft. Aircraft engines are more reliable also for lots of reasons one being cooler temps and less loads their is no gear box or wheels to turn on a hard surface. Walbro WA-164 is a good carb for your 25cc's through 32cc's anything above that I have no experience with but you can the the walbro web site for the size zenoa use on there model engines as reference. Good Luck.