Check your plug first....see what color it is. Shouldn't be white or light grey. Should be tan to chocolate brown or a slightly oily black. If you are running too lean it will seem weak and get hot quick, too rich and it will have a good pull, but when you hit cruise or WOT it could "4 cycle".

Now, what do you mean "The clutch is not covering the air hole and the throttle does not cover it too."?

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