Ok. I got it out and pushed in the new seat. No screen, though, because I didn't order the replacement yet. Here's a pic of what looks to be a difference in depth between the original and replacement seats....
https://picasaweb.google.com/lh/photo/agrpnXM8OkreTDks6ER89tMTjNZETYmyPJy0liipFm0?feat=directlink
And here's a pic of the old seat.
https://picasaweb.google.com/lh/photo/eUTyZZ6u78QgXocfji9-V9MTjNZETYmyPJy0liipFm0?feat=directlink
It's pretty beat up, but didn't actually look that dirty. The plug did have a bunch of gunk on it when it came out, though. Nothing flaky, just like little green/white mud. All the inlet tubes freely flow clear carb cleaner when I spray in them. So what I'm wondering is... Do I HAVE to drill out the other ones and use the replacement seats that came with my rebuild kits, or do you guys thing I can leave the originals in there. I know there's a "should" factor here, and it's not like the bike is going anywhere with the carbs still in a million pieces. I'm just wondering if I could have actually left all of them intact and run it like that. I haven't ordered the replacement plug(s) and screen(s) yet, so I'm going to defer to the judgement of the board on this one. Now that I have an idea of what it takes to get them out, I'm willing to go after the other ones if I have to.
I'd replace them but it's really your call, you're the man 'on the ground.' Be very careful when you press the new plugs in, it's very easy to crack the carb bodies.
As for the different depth, did you get OEM seats or aftermarket? Compare the new beside the old for a difference.