Not firing on 3-4?

[KenRocks]

So I have this 98 kat 600 that I picked up from a guy down the road...it's been sitting for...awhile? Wouldn't start when I got it...cleaned the carbs, reassembled, charged the battery and it started up, but it runs rough. With the bike warm and the choke off, the idle sits at 1k...the screw is all the way run out so I cant get it any higher to the recommended 1200. When I twist the throttle hard, it hesitates, then catches up...if I twist it slow, itll usually keep up after a second or so.

After running it for a few minutes, I had this feeling that it might not be firing on all cylinders, so I shut it off and felt the headers. Number 4 was warm, but I could leave my hand on there indefinitely. 3...hotter...could leave my hand on a few seconds, but then it started to sting. 2...holy god instant pain.

So...I think that 3-4 arent firing, but maybe are warming up off of the gas from the crossover? I read in one of the stickies how it is a common fault for two adjacent cylinders to fail at the same time (but not due to coils, cause those arent adjacent?)...does anyone know what might be causing this?

[Sturg]

My first idea is to double check that all the butterfly valves are moving with the throttle. If not my guess is just A/F screws... May be such that they're too lean/rich while the other 2 are in a good range. May have to tinker with them, there are guides to carbs that would be more informative than I.

[KenRocks]

Well...I'm confused now.

Finally found the right sized socket to pull the plugs...figured since I hadn't checked spark yet, that might be a good place to start. All of them have a strong, blue spark.

Found that kind of strange...reinstalled them, then decided to let the bike run a little while and check the headers again. 3 heated up rapidly this time. 4 is still cold.

If I left that vacuum line coming off of 4 unplugged, would that cause this?

[DumbLuck]

absolutely. the sync ports needs to be capped, and the extra hose from #4 that runs to the petcock (to hold it open when the skoot is running) needs to be solidly attatched and not leaking. vacuum leaks will make a skoot run like crap or a cylinder not fire. did you do a visual sync, and then a vacuum sync after "cleaning" the carbs?

[KenRocks]

Didn't do the visual synch...but I made a manometer out of two bottles like I saw on the walkthrough here, and I was intending to do a vacuum synch later.

The oddity is that the idle isnt bouncing or anything like that..it sits at 1k pretty solid. I started it again earlier and plugged the vac line off of 4 with my thumb to see if sealing it/opening it would do anything...didnt seem to really make any difference, though I could feel the suction through the hose. I'll run it again later with a set of vice grips on the hose to make sure its all the way sealed.