RCIGN,
I make it 3lbs 4oz (with original muffler, RCIGN prop driver and walbro carb, - no prop, no coil).

I'm now fitting a Walbro carb, (trial) and I figured that the pump would still work, with the intake vacuum creating a negative pulse, and then a positive pulse being provided when the inlet valve slams shut, (because the kinetic energy of the mixture builds up a positive pulse, as it keeps on coming into the inlet tract.)

Could this possibly be how the original carb works too? - just a thought, - (open to discussion ).

I agree that the restriction needs to be removed from the inlet tract, - I intend to have a tapered tract between the carb and the port on the engine.

BTW, - All work on the project has ground to a halt here, - I severly damaged my thumb ( at work, - not by a prop! ), and now, they have had to amputate the top half, so that's slowed things down considerably! - I've also got to find a way to use the sticks again!