Carburetor shaft seals
The rubber and felt seals found on Keihin/Honda carburetor throttle and choke shafts do not seal vacuum, they seal dust. Therefore, an engine performance issue cannot be solved by replacing them. While many on the Internet want you to believe that running problems can be solved by new seals, it just isn't so. Replacing the seals won't fix anything.

Vacuum leak detecting
Related to this is the technique of spraying substances onto the intake manifolds to check for vacuum leaks. This tactic is not as conclusive as many think. The reason is carburetors have openings to atmosphere at various places around them. You can occasionally get a response to an aerosol simply from that fact. A better way is to use the classic "more air/less air" test which by altering the restrictiveness of the air intake system highlights where the issue lies, whether with the engine, the ignition, or the carburetors. The more/less air test is also a good way to determine correct carburetor jetting in relation to engine modifications or altitude.

Bench-syncing carbs with wire or drills
Bench-syncing carburetors is a must after work has been done on them that includes disassembly. However, the Internet is good at taking things out of context, and so here too. At one time, using a drill bit or wire was an accepted method of bench-syncing the carburetors on variable venturi carb equipped pushrod-engined Brit bikes. Their carburetors' slides could not easily be damaged by this technique. However, this method does not at all translate into modern carburetors. Later constant velocity carbs have exquisitely-machined sharp-edged throttle butterflies. Passing anything under these can easily ruin them, and guess what--they do not have part numbers. I replace several each year, but these parts have to come off of other carburetors, so they're precious and expensive. Constant velocity carbs are best bench-synced by using the bypass ports. Variable venturi carbs by eyeballing the heights of their throttle slides on the engine side (not the air filter side). Both are easy and effective techniques that do no damage to parts.

Swapping carburetors
In some circles, folks talk a lot about putting a carburetor from one bike onto a completely different machine. We're talking stock production carbs and stock bikes. Grief awaits when one decides to put a carburetor onto a bike that came off another bike. The problem isn't the carburetor per se, it's the jet needle. Honda worked hard to make the jet needle perfect for the host bike. This all-important part together with its mate the needle jet, controls the bulk of the carburetor's metering. It determines the character of the carburetor. And unfortunately, seldom will it translate to another bike. Worse, the original jet needle can't easily be exchanged for a one with a different taper, as there are no alternate parts because the host carburetor was massed-produced to a price and thus never meant to be modified. Consequently, no recalibration parts are available for it from Honda. Carburetor manufacturer Mikuni from the beginning supported maverick carburetor use by making available catalogs full of alternate parts, at least for its earliest VM series carbs found mostly on offroad bikes, but much less so for its later production carbs. By contrast, Keihin, the maker of Honda's carbs, has only in a very limited way supported even its racing carburetors with alternate, tuning parts, let alone its production carburetors. Can you ultimately find a jet needle from one model Honda that will work in another? Maybe. But you'll have to devote a lot of time and energy to this. A lot of trial and error. There are folks on forums who have spent years trying to solve issues on their transplanted carbs and are still not satisfied with the results. Be aware of the pitfalls. You're better off fitting a generic racing carb than attempting to make a carb from one model Honda work on another. Better yet, work at getting your original stock carb to work properly. It isn't that hard, and once it's right, the stock carburetor often outshines all the alternatives.

Sta-Bil
Those of us who are older can remember how gasoline used to smell. Potent. Definitely very different from what it is now. Three chemicals used to be included in gasoline refinement: benzene, toluene and xylene. One or more of these was present in all pump gas and they enabled that gas to last as long as two or three years before it started to go bad. Benzene was outlawed when it was found to be a carcinogen. Toluene and xylene were eventually linked to liver and kidney damage. You can still encounter toluene in some racing gasolines. It gives them that model glue smell. These chemicals are called aromatics. Their final removal from gasoline cooincided not only with health concerns but also with stricter automotive evaporative emissions laws. Everyone took for granted their benefit of making gas last long. And it doesn't now. And this has nothing to do with its ethanol content. The OEMs have published in their owner's manuals warnings that today's gasoline lasts only a very short time--as little as three weeks in some climates. Consequently, we have to be proactive and add fuel stabilizer to our gas. Full-time. With every fillup. There is no way around this short of using one of the racing gasolines, a choice that some bike collectors make but which for daily use would be extremely expensive.