I assume you mean the float valve, not the float?
After trying aftermarket kits on several bikes in the late 70's and early 80's I gave up on them. There's apparently a lot more to making a jet than meets the eye: orifice smoothness, length of sized orifice hole, size of counterbored hole - these are my guesses as to why Keihin jets are consistent and aftermarket ones... not so much. The needles can at least be measured easily and compared to OEM but I've never needed to replace a needle with aftermarket, I have a few used carbs I can strip parts from.
I haven't looked lately (kinda retired from working on other peoples bikes) but Honda still had carb gasket kits and float valves for our engines a few years ago. The float valves particularly were used on MANY models and may still be on some new bikes/ATVs/lawnmowers/etc. Unless something has changed, the O-rings and bowl gaskets (another O-ring) are NOT ethanol stable so you should try and get viton. The bowl gasket works OK but swells and needs a day drying out after removing the bowl to shrink back to size, the fuel crossover O-rings tend to split so fuel dribbles out onto the hot motor. Having to disassemble the rack for that is a major PITA. Or use ethanol-free gas if available.
The price for OEM float valves is high, but they work. Same with jets, if available from Honda or anywhere as genuine Keihin... worth the price premium. Jets pretty much never wear out, the main jet and needle can wear but it takes a lot of miles. For tuning I have a fair selection of mains and pilots for some models, there are apparently sources for Keihin parts (jetsrus.com - read this
http://www.jetsrus.com/FAQs/FAQ_genuine_jets.html). The air/fuel screw is not critical but your "best" setting probably won't match the Honda spec since the taper is not exactly the same.
Of course aftermarket kits may have improved with no reason to avoid them now.
The cost difference for me was less than the time cost of additional carb stack out/in cycles to deal with when tuning (or when a new set of float valves leaked after a week or two). Once (or maybe five) times bitten, next time shy. For a single or dual carb motor where they can be out and back in in a minute with no blood loss, OK. For quad carb sticks, ossified spacers, and sardine can fit intake boots, I will go with OEM.
