I have a 91 gs500. I drove it to work with no problem. When i parked it at work I lock the wheel and left it in park. 8 hours later battery is dead. I then got it trailered home and charged the battery. Started up the next day and it sounded off ( not as throaty crisp as before) very sluggish in low end (I know it not the gs strong suit). I have to run it on full choke or it will stall. I drove it around for a couple miles and it started to back fire then stalled, lucky for me it was in front of my house and i coasted into the driveway. I Changed the oil, spark plugs, and fuel filter before this all started. I put in a clear fuel filter in so i can see whats on, when i put it on pri before i could see the filter fill with gas, now it doesn't fill with gas.
imo, could be one of two things.
1) check that the fuel filter is installed in the correct direction, they are only designed to work one way. if you have it in reverse, no fuel will get to carbs, or else very slowly. so check the direction of the filter.
2) otherwise it could be a problem with the petcock. it may be blocked or not working properly, i had the same problem, and in my searching found other threads on the topic. if it is the petcock:
you may have to pull off the tank, the airbox, and the hoses that go from the petcock to the tank. for testing reasons, i would leave the hose on the fuel chicken, but remove it from the tank end. two other hoses to remove also. go ahead and take those off the petcock end.
there is one bolt that holds the fuel chicken to the frame, remove it and pull the chicken out ( :nono:, dirty minds!) remember how i said to leave the hoses from the tank on the petcock? once it is off, you can experiment by blowing on the hoses (might want to rinse them, might still taste like gas though). test the petcock by changing the position of the switch and blowing on the hoses...you should be able to figure out if it is working right.
if i remember correctly, i think in prime mode, you should be able to blow on the reserve hose and get air through. same for reserve, i think the main hose only works in "on". dont quote me on that.
if you find that it is blocked, you may need to open it up. you may need to remove the backside with the 4 screws. be careful because there is a gasket and a fragile diaphram, if they are damaged you could end up with a leaky petcock. the switch is held on by a small shiny metal bracket that clips on over two tabs. use a small screwdriver to pop it off carefully. dont lose a small spring that keeps tension on the switch. the white plastic peice inside is the valve itself. you may need to pop it out from the backside.
clean it and put it all back together. test again. note that the switch only fits one way into the white plastic valve, it looks like it can go in upside down but one end of the fitting tab is larger than the other. you can barely tell, but it wont fit the wrong way. also be sure the little metal tab shows prime at the top, otherwise it could get confusing.
i took mine apart, and for some reason it would work without the tension spring, but not with. somehow the valve was getting bound up, or the switch was not interlocking correctly. when i installed it back on the bike without the spring, i got fuel through prime to the filter, but it also leaked :icon_confused:. i took it apart and put it together correctly again. i believe if the iwhite plastic valve gets worn where the switch interlocks with it, the switch can slip, and not turn the valve at all. this may the problem you have.
be very careful and push firmy on the switch while turning it, and you should be able to make it catch and turn properly. personally, i think the oem switch is garbage. they might work well new. but the rest of the bike will outlive it. im going to do the pingle petcock mod or find another way to fix up the system.
oh, and im just gonna throw this in as well for anyone with similar probs:
i prefer clear fuel line over the thick plastic hose. the clear lines make it easier to see which hoses are and arent getting fuel through them. also if you get black hose that is too thick, it can be very hard to put both hoses on the tank. its a tight fit. i believe the proper size for the hose is 5/16th, i have 1/4 inch hose on my gs and its a VERY hard fit to get on, id say too tight.
I know you had the plugs replaced before the problem , but just check them now if they aren't fouled , if you tried restarting the bike after battery died it might have built up carbon on the plugs