Yes, make sure the doughnut isn't pinched or rolled, That's easy to do when reinstalling the carb.

 

Yes, I put on a new one and greased it. Anybody ever send theirs out to the "expert" to have it Sonic cleaned and "remanufactured" there's a guy on eBay $125.

 

What's it idling at when hot? Should be about 1000 RPM. The idle screw may have backed out.

 

The problem is that it's inconsistent. The idle hangs sometimes, is low sometimes and is high other times. It varies stoplight to stoplight.

 

Redneck these guys have covered it here and it will more than likely be a fix in the wall of text here but there's obviously too much information for you to take in .
The fact you can't get idle consistency says it's not carburating properly at that point any way it's out of the right range , so yea if it was in the right range would it not idle ?
Here's a guide http://www.nightrider.com/biketech/c...leshooting.htm there's stuffin the site that will help too.
Do you know how to check the needle and seat and to set float bowl height ?

 

My fear is that the idle mix needle seat is damaged and I don't know how to check it. The mix needle is new and undamaged but i'm worried about the seat.

As I said, I had a situation with a carb once that wouldn't work no matter what and ended up replacing the body and everything was fine. I think that's where I'm at. I've confirmed the one-way check ***** by blowing and sucking (yeehaw) but that doesn't mean they necessarily work consistently.

 

What is an idle mix seat ?
Do you mean the mixture screw ?
The needle and seat is where the fuel comes in to the carby.
Take off float bowl with fuel off, push bowl up slightly , turn fuel on , if it dribbles it's fuked
if not it's good lower the float till the fuel comes through remember correct float height is when the floats horizontal edge is parallel to the carb where the bowl mates back on.
The tab that seats the needle seat is where you adjust it. the thing that looks like a mini pencil with a tiny pull ring on it is set by the tab .
And it's finicky az fug in there too.

 

The idle mix screw has a seat cast into the body which,. I understand, can be damaged. That's what I was thinking of

 

If you screw it all the way in till it gently seats then out 2 1/2 turns that's a good place to start for tuning if everything else is right . The point at where it seats can only be damaged by a bent mixture screw but that won't happen as you wouldn't get thread to screw it in. If you get good take up when screwing it in, ie no lateral movement till it lightly seats it's fine .
But if the needle and seat that supplies fuel to the carb bowl is out, the steps I explained in my post before is how you make the fuel level in the carb right cause if it's not every other setting won't work.
If you set the needle and seat to how I explained to , we then go to step 2.
It's on you man.

 

Take a flashlight ( don't use a match!) and look inside the tank for any debris.