I have bought a few carburettors over the 6 years i've been playing with these engines, and have a few carburettors set up with 3 jet size increments that are around the average of what my engines normally use, eg, one carburettor with a No #73, No #76, No #79, No # 81
For the most part my engines (using Australian lower eastern states 98 octane fuel, which is equivalent to American 93 octane fuel) run optimally using a Dellorto No #76 main jet. I have had one engine run optimally using a No #70 main jet and another engine run optimally using a No #86 main jet, but for the most part, they seem to run best around a No #76.
It's a lot quicker (and less messy) to change the jetting (of a float style carburettor) by simply unbolting one carburettor and bolting on another with different jetting, then perfectly optimising the jetting once you know which way you need to go; using 1 unit jet size increments.
From past experience, i have paid around $3.50 (per jet, in Australian money, and i must have around 30 jets, so it works out to around $100AU for all of my jets.
My current engine uses a No #77.
The only reason why i am using the NT carburettor is because i've been too lazy to put the Walbro style diaphragm carburettor back on the engine, but i'll endeavour to put it back on in the next week or two.