Modern Vespa

Hi guys when a 2 stroke engine is designed is there a formula for the volume/size of the inlet port and (crankcase) volume , the transfer port , exhaust port ? and i assume the returning exhaust charge is part of the calculation?

what i sort of mean is by reducing the diameter of the inlet port of a generic set of crankcases ,how does it affect,the velocity or quantity of fuel entering the cylinder via the transfer port?
thanks
george

All else being equal, narrowing the intake will increase the velocity slightly but reduce the amount of the charge entering the cylinder over a given amount of time. There is a formula for it. Try Jennings.

I think it's in the tuner's handbook I sent you

Yeah, Bernoulli's Principle.
By reducing the inlet, you would increase the velocity but decrease the pressure. That's not really what you would want for this engine, because the higher pressure is what helps get more f/a mix into the crankcase.

yes......................... its your fault LOL i read then need a cogent paradigm to absorb, i,ve sent dozens emails asking for information on crankcase differences but have met with.............................no response ,oh thats not exactly true no answers but would i like to purchase something from the catalogue !!
many thanks
george