I bought my first motorcycle, a 99 GS500, back in November with 5600 miles on it. The bike was in great shape, bone stock, ran beautifully and I got it for a good price.
Now it has 6200 miles and refuses to work.
I'll give the bike some choke and start it up, and it idles evenly. As it warms up I'll close the choke lever... and the idle speed slowly falls and the bike eventually dies. If I give it any gas at all while it's running it bogs down hard. With enough finesse I can get the bike up to about 6000 rpm where it stops and refuses to rev any higher. After the bike finally quits it refuses to start up again, until I eventually get fed up and park it. The next time I come out to start it, I give it choke and it starts fine, then slows and dies again.
I've pulled apart both carbs and they looked pretty much spotless. There was some grime in the bowls, which I cleaned out, but all the jets and the needles looked perfect. . When I pulled the original plugs they were both pretty black. I replaced them and now the brake-pedal-side cylinder looks flawless but the shifter side is still dark. I re-set the float heights today and the bike is still doing the same thing. Neither plug is wet or smells like gas.
This problem has kind of showed up gradually over the last 100 miles, but only very recently has it been unridable.
This is my first bike, and while I know my way around an engine fairly well I have no experience with carburetion and little experience troubleshooting problems like this. I've pulled individual plug wires before so I know the bike will run on one cylinder, so I don't see how it could be a carb issue... yet the plugs tell me at least one if not both are running rich. I did screw up a couple times when I first had the bike, left it on prime and had gas leaking out the airbox drain hose. Right about then was the first time I noticed any trouble... but that was probably due to flooded carbs, right? And surely if it had screwed up anything I'd have corrected it when I pulled the carbs apart?
I've spent a fair bit of time searching the forums but nothing I've read has been too helpful. Maybe it's just my complete lack of experience, and maybe I'm missing something obvious, but I'm honestly stumped.
May the wise men of GSTwin share their knowledge with a humble newb with no clue. :bowdown:
Quote from: FBS on January 07, 2009, 09:26:27 PM
I bought my first motorcycle, a 99 GS500, back in November with 5600 miles on it. The bike was in great shape, bone stock, ran beautifully and I got it for a good price.
Now it has 6200 miles and refuses to work.
I'll give the bike some choke and start it up, and it idles evenly. As it warms up I'll close the choke lever... and the idle speed slowly falls and the bike eventually dies. If I give it any gas at all while it's running it bogs down hard. With enough finesse I can get the bike up to about 6000 rpm where it stops and refuses to rev any higher. After the bike finally quits it refuses to start up again, until I eventually get fed up and park it. The next time I come out to start it, I give it choke and it starts fine, then slows and dies again.
I've pulled apart both carbs and they looked pretty much spotless. There was some grime in the bowls, which I cleaned out, but all the jets and the needles looked perfect. . When I pulled the original plugs they were both pretty black. I replaced them and now the brake-pedal-side cylinder looks flawless but the shifter side is still dark. I re-set the float heights today and the bike is still doing the same thing. Neither plug is wet or smells like gas.
This problem has kind of showed up gradually over the last 100 miles, but only very recently has it been unridable.
This is my first bike, and while I know my way around an engine fairly well I have no experience with carburetion and little experience troubleshooting problems like this. I've pulled individual plug wires before so I know the bike will run on one cylinder, so I don't see how it could be a carb issue... yet the plugs tell me at least one if not both are running rich. I did screw up a couple times when I first had the bike, left it on prime and had gas leaking out the airbox drain hose. Right about then was the first time I noticed any trouble... but that was probably due to flooded carbs, right? And surely if it had screwed up anything I'd have corrected it when I pulled the carbs apart?
I've spent a fair bit of time searching the forums but nothing I've read has been too helpful. Maybe it's just my complete lack of experience, and maybe I'm missing something obvious, but I'm honestly stumped.
May the wise men of GSTwin share their knowledge with a humble newb with no clue. :bowdown:
Good start - it sounds like you've already checked the basic stuff that would otherwise have been recommended (float height, clean carbs). Since your bike is flooding on PRIme, this is an indication that the floats are sticking or the float valves are worn. Did you check the condition of the float valves when you took apart the carbs? The tips are rubber-coated, and can become damaged (torn) or worn (too "pointy").
You can use this easy method to confirm float heights now that the carbs are reinstalled. This should help to determine if the floats are still sticking/worn:
http://www.bbburma.net/FloatHeight.htm
http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/FloatHeight
I would also suggest checking carb balance
http://www.powerchutes.com/manometer.asp
http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/5CarbSync
and valve clearances.
http://cgi.stanford.edu/~sanjayd/gs500/Maintenance/CheckValves
Good luck! Keep us posted :cheers: