And therein lies the problem...The hole in the carb for the pulse is usually not in a good place to line up with a hole that could be drilled through the reed block...The reed block with a hole it it is the cause of some of the problems with the RCS 140..the thin aluminum plate under the carb bends..A bent plate doesn't seal well and the pulse leaks out..No pulse, no pump..A fitting somewhere in the case, or even in the transfer port, is a better way to get the pulse to the carb...The chainsaw carbs DA uses are made just that way, the hole for the pulse is not drilled out in the carb body and the backplate has a fitting in it...Many of the carb inslulator blocks don't have enough space under for the carb to route the pulse to the hole in the carb...The rotator blocks made for the Zenoah engines are a good example, the pulse passage in the block is within 3/64' of the center hole..Any mismatch between the gasket and the hole results in a pulse leak and less than adequate fuel pumping....With a fitting in the case the carb gets the full pulse all the time, even if the carb is slightly loose on the block..
I have tried some different ways to route the pulse to the carb, always came back to the fitting in the case on most engines...
Another way to do it....Make a lathe fixture to hold the carb so the bore is centered...Turn a 360 degree groove about 1/16 wide in the base of the carb about 1/16 deep, with a diameter that would cover the pulse hole.. The pulse hole will get the pulse no matter which way the carb is rotated..Would take only about 30 seconds once the fixture is set up and the groove tool made..You could do 100 carbs in a short time...
BUT...The carbs would have to be the ones with the pulse hole already drilled in the base..(Most are)