With large ports and a long-duration cam, the bottom end RPM will tend to be very rich. This is why these types of engines must be 'revved out' on starting lines with engines running and that sort of thing: it's also the dragracer's nightmare. Below the cam's active RPM the carb will suffer poor mixing from teh back-and-forth airflow through it as the intake spits back toward the carb until the engine is running fast enough for the inertia of the incoming fuel-air mix to overcome the back-toward-the-carb air impulses caused by the early-opening cam.
That said, if I were going to build and run such a beast...
The 500/550 top end suffers this low-RPM richness already in stock trim, begging for a shorter intake tract before it could work well below 2000 RPM. That just isn't practical as the engine heat, transmitted to the carbs via the metal intake manifolds, will then boil the carbs' fuel, which is why these are high-RPM engine designs - to stay cooler when moving. This is also an issue with the 750 when ridden in heavy, slow traffic on hot summer days: my own 750 has many times boiled the fuel in the carbs on 100+-degree days in those conditions. And IT has rubber boots between the head and carbs!
Those carbs are also considerably larger than the intake valve's open area, so the low-RPM range will be "soft" in its mixture, tending toward richness, because the intake tract spitback from the overlap of the cam will slow down the airflow enroute to the engine. This will make the carb mix as if the engine were running slower than it actually is until such RPM as the cam 'comes on' and starts making the intake flow linear-ish again: this will be in the 1/3-of-throttle region with the pieces you have assembled now.
If I were to roadrace this arrangement: to get it to start, you'll need dextrous manipulation of the choke (playing with it) over a leaner idle mixture until the engine warms up a bit, enough to run on the lean idle mixture. Then you'll need to (multiple times) fiddle with the needle position in the carb until it will transition from the idle circuit to the slide-controlled region, as the engine will tend to feel 'flat' right there in the RPM range. Being a smallbore engine makes this even more of an issue, so the intake tract to the carbs MUST be considered to be a part of this solution - and, open intakes or "pod" air filters are the worst choice possible, as there needs to be a pressure difference between the float bowl (at atmospheric pressure) and the flow in the body of the carb (lower pressure than the bowl) or else the fuel will not aerate. Then it won't burn well either, making for blackened sparkplugs and no throttle response. Sort answer: put the stock airbox back on for starters, then consider the way it is fed air, and the type of filter used inside: brand-new paper filters work pretty well, while gauze, very lightly oiled, works wonders above 7000 RPM and seldom needs servicing.
I'll get off my toolbox now...
