Hello, this is my first post here, so be kind :D
So, I have a 1991 GS500 and a few days ago I went for a ride after it been standing for 3-4 weeks. Battery has not able to start the bike so I went downhill and push started and it ran fine for about 3 km (Around 2 miles) and it started to fail.
I thought that it was running out of fuel, so I stopped on a fuel station. I opened the fuel tank and it was pretty much full...
I tried to start the bike and I had a flat battery. Tried again to push started and nothing...
On that night, I recharged the battery and on the next day gave it another shot and it still won't start. The starter was strong but the engine wouldn't start. I changed the spark plugs for new ones and nothing..
I have the day off on Wednesday and I'm going to try to clean the carbs, changing the fuel filter and changing the fuel for a recent one.
I don't know if it's going to do any difference, but any other suggestion is welcome
(Not english native, so sorry for any errors :) )
Whatever you do, don't spray carburetor cleaner onto the carburetors, or especially not INTO them. You can damage or destroy the rubber diaphragms that way.
Sounds to me like it burned the fuel from the float bowls and then ran dry. Could be the petcock is not opening (it's vacuum operated) because either it's vacuum line is disconnected, you have a major vacuum leak, or it's just defective. Try turning it to PRI and see if it starts. If so, then that will get you looking at the petcock as the problem. BTW note that just because the petcock doesn't open doesn't mean it's defective. It's far more likely that you have a vacuum issue. It just manifests at the petcock.
If the petcock/vacuum is not the cause then it could be a float needle valve stuck closed, unlikely they both would stick, but possible. Could also be clogged pilot passageway in the carb or clogged pilot jet, both are kind of likely. You are starting it with choke all the way on, right? If so that should rule out pilot jet problems, because the choke is actually a jet that is manually opened so if it won't start on choke then it's not primarily a pilot circuit problem.
In any case it's much easier to just fix everything at once than it is to try to diagnose it. Do this: https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html
It could also be ignition. That's a whole different set of steps to diagnose. If it just died suddenly while otherwise running fine rather than sputtering or trying to run, then I'd suspect ignition. Something that drives both coils, since it will run, just badly, on one cylinder. That'd be igniter, signal generator, wiring, ground.
Good luck-
Actually I bought a carburetor service kit, because its a 26 year old bike and who knows if it ever was replaced....
I'll start from there and I hope to come back with good news
A small update on this subject, I dismantled the tank and found a drain tube coming from the tank stuck on the chain..
On the side connected to the tank, it was completely clogged
I don't know if this was enough to prevent the bike from working, but I don't think so.. I haven't had the time so check the rest, but as I said before, I'm going to check and do a quick service on the carbs. (https://uploads.tapatalk-cdn.com/20180331/cee690f882b00b12eac03453d77b51b2.jpg)(https://uploads.tapatalk-cdn.com/20180331/f81426f8f7afeb3cd94e86eb96f38d80.jpg)
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