1981 XS400 Special not (really) starting

[bchiu]

Hello experts! I purchased a pretty complete 1981 XS400 Special the other day for a couple bills. It wasn't running, so I brought it home, hooked it up to my battery charger and was able to get what sounds like the beginning of it trying to start, but then would quickly die. I've tried both the electric and kick start. The person who sold it to me mentioned that they had recently cleaned the carbs but they needed to be "calibrated." I'm assuming they meant that they needed to be "synced"? I posted video of me trying to start it.

Some quick background on me: I'm located in Houston, TX. I'm also a complete newbie, to both riding and motorcycles, but pretty adaptable in the shop and researching how to things online and whatnot. I just bought a haynes manual and found the downloadable service manuals, but I'm hoping you guys could give me some tips on where to start diagnosing the problem.

Thanks for any assistance you guys can throw my way!

 

[Lego]

I would clean carbs once again. You never know how did PO clean them. During that cleaning, check which jet sizes are in there, you can find here what sizes are correct. After rebuild, bench sync them. Try to start, and them sync them with manometer. There is 2 adjustable things: pilot mix screw (2 or 3 turns out from lightly seated position is a good start) and idle speed screw(throttle stop) that can be adjusted to get good idle rpm, you can play with it later.