Could this be why I'm running on one cylinder?

[MGXS400]

I'm digging into an 81 XS400 I just purchased and I thought I'd explore the carbs a bit. I found a piece of rubber between the two posts that hold the float so I pulled it out because it looked like it was keeping the float from freely moving. I then realized it was some kind of glue that was keeping the cracked pieces together. This was in the left carb and I've been trying to figure out why the left cylinder isn't firing. Could this, combined with dirty jets, be the cause or part of it?

Also, could anyone tell me which carbs I have. I think they are BS34 but I really have no idea, this is all new to me. Here are more pictures:

 

[willem]

to answer your thread title: Yes.

I'm not an expert on carb ID, unfortunately. But if I were you I'd fix the carb back up with some JB Weld or some other kind of epoxy that withstands being around fuel all the time. Sounds like the person who fixed it before didn't use the right kind of glue. I can totally see how that glue disintegrated and started clogging up your jets, as well as your float not being able to move as it should. Both can mess up your mixture, which causes running on 1 cylinder

 

[arfstrom]

One of the tell tale signs is the float bowl drain. That is the same type of carb that is on my 1981 4R4 series Special (heritage, only via association of the series #, not marked heritage) BS34 Carb.
Please check out the popular Carb guides, www.amckayltd.com/carbguide.pdf‎ and

Of course the Thread that is marked "Broken Carb float holder How to Fix"
http://www.xs400.com/forum/showthread.php?t=5110

He put all his photos on Flicker, and used Drill press to vertically drill in a support dowl, and glued it in. I have seen smaller drill press's for about 40 bucks at our (US) Menards type locations.

Here is the paragraph from the first link. (go though it, just cause its marked for the 650, they have 4 of the BS34 carbs. we only have 2.

The floats hang from a pin passing through two posts cast into the carb body. Care must be taken not to damage the posts. A broken post can be repaired by carefully
drilling small matching holes in the post and the carb body and pinning the pieces
together, using JB Weld as an adhesive; but this is a touchy procedure, and damage is
entirely unnecessary. Don't try to beat the pins out!

and that Youtube video with two parts, shows, and discusses the hazards of punching out the pin and the towers breaking, 9 minutes a piece.

Part 1

part 2