new 70cc

hey i got a new 70cc motor to replace my 50cc motor that had done over 5000 kms. I am running in and understand that it will get more power after run-in.
But I have no top speed so i drilled some holes in the cover and it did improve, I can ride ok but i would like more top speed it seems not to be getting much air.
Could anyone help me get some more speed and make it breath a bit, Thanks

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.

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