How stuck is the float bowl? Try to tap it to break it loose then you can get inside.
Ken
Unless you meant something else. 
I have tapped it numerous times and it always works (stops the leak) for awhile then comes back sometimes as much as months and months later. The leak is intermittent (no rhyme or reason to it occurring but it is usually in the mornings after a hot day/ride). Thought I should stop it once and for all instead of hitting it with a screwdriver handle each time. It is always on the #3 carb.
If it has been a couple of years replace those needles and seats.
It has been over 4 years
While pulling the carbs and giving them a good cleaning is never a bad thing, there is also quite a bit that you can do to troubleshoot leaking float bowls with the carbs still in place. I believe on most of these carbs the float valve and seat can both be replaced just by removing the bowl. Another cause can be a "dimple" that forms on the float tang after decades of use. This can be removed and carefully sanded without removing the carbs as well. At least all this can be done on my 657a (750K3) carbs.
Just thought I'd mention it.
I can't really help with advice on the aftermarket parts. I rebuilt mine from the partsmore carb rebuild kit. Some of the replacement parts in the kit appear to be genuine Keihin, but others aren't quite as clear. So far I haven't had any carb issues that I can blame on these carb rebuild kits.
Aaron
Can I get to the #2 and #3 on a CB550 without having to join the circus to twist into the spaces I would need to for removing the bowls? I was also going to put on new intake manifolds so thought pulling the carbs would be a good way to go since I have to for that operation
I've gotten the (non-rubber tipped) inexpensive ones from PnM... they work for me.
I've had rubber ones degrade and fall apart on me before... too much ethanol?
Were they the $8.50 ones I am looking at? That would be perfect. I too was looking for the non-rubber tipped, especially if they worked well
