Re: new 70cc
Check your plug first, to determine where you are as far as the mixture is concerned.
You want to get it close to brown, or just slightly black. The engine will require a little break-in just like the 50 before it makes full power.
Does it four cycle and never clear out when you turn the throttle to wide open? Too rich.
Does it run good, and lose power at anything over two thirds throttle? Too lean.
If too lean, you may have the common air leak.
Check the plug first.