1980 GS550L no longer starts

[Guest]

I'm definitely a beginner mechanic and this forum has been awesome. I'm at a bit of a loss and finally reaching out for help with this issue.

I purchased a 1980 GS550L at a great price in non-running condition. It was running last year but was not winterized and would not start. The intake boots were shot - replaced those. Had a mechanic friend of mine rebuild the carbs with a kit. He did not de-rack or soak them. Replaced 2 diaphragms. New battery. Petcock replaced last year, still functions. Jet screws set to 3.5 turns out (factory settings). Runs pretty well! Planning on vacuum syncing the carbs very soon.

I had been riding the bike for the last 3 days without major issues. Today I was riding and it died on me. I thought it was the petcock because I had some previous issues with fuel delivery. Replaced the petcock vacuum tube. Confirmed the petcock was working and even tried an IV instead of the tank. When I loosen the screw on the carb bowls gas does flow out. The sparkplugs do spark but are dry when I remove them (they also look fairly dirty). I would presume this means there is an issue delivering fuel to the cylinders. The bike would initially give a half hearted attempt to start for a split second, now nothing.

Any ideas would be greatly appreciated.

[Nessism]

Check the Newbie Mistakes thread linked in my signature and start going down the list...

[barnbiketom]

mechanic friend of mine rebuild the carbs with a kit.
He did not de-rack or soak them.

2 mistakes in 2 sentences....

[PTB4Life]

Update:

So I've started going down the list and found a couple things that are likely causing problems. I drained the gas from the tank through the petcock and noticed there were trace amounts of rust residue that settled to the bottom of the container. This would be residue that made it through the screen in the petcock. I pulled the petcock and drained the remaining gas and there was quite a bit of rust, even some chips and chunks that came out. I will be researching how to properly clean the gas tank but if anyone has advice I will be happy to take it.

I drained the bowls on the carbs and used fresh gas in the IV. It wouldn't start on gas, but a little bit of starter fluid in the air box got it running. I let the bike run for about 15 minutes before trying to set the idle. The bike would struggle to idle below ~1300rpms. I noticed that at low RPMS an audible clicking or knocking could be heard from the engine. The source seemed to be one of the cylinders on the right side. My guess is that some residue from the gas tank got into the carbs and is causing one of them to not supply gas to the cylinder. Could this be the source of the noise?

I will be pulling the carbs and rebuilding them properly myself using the provided tutorial. I should be able to get the original parts back to avoid using the kit that was installed, though I know that a couple of the jets were damaged in the process.