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My '92 GS500 has not survived its 6-month lockdown, and I've had it trying to make it run. I'm using one of my lifelines.
This bike has maybe 5K on it since a top end rebuild and has been pretty much dialed in but fell to only occasional use after I got my Triumph a couple of years ago. I had just sorted a frustrating tuning issue in the summer before I had surgery and couldn't ride a couple of months and then I wrecked my Triumph and had my foot in a cast and couldn't ride a couple more months. Basically that means the bike was running perfectly in June when it was parked and then in late November when I got back on it, it had gone south. I always run ethanol-free fuel in it and even though there was no fuel stabilizer in it when it was parked, it at least not ruining its own o-rings with ethanol.
The engine is basically stock. Has a UNI air filter, shortened Yoshimura muffler and header wrap. I think it's currently jetted 125/40 with one washer on the needles. In June it ran perfectly.
OK, so when it came off hibernation it didn't want to idle. Everything started and ran ok but once it was warmed up and you turned the choke all the way off, it would die if it tried to idle. Also it wouldn't start unless I put it on PRI, and sometimes wouldn't run unless on PRI. I figured maybe the cabs were gummed or clogged up, and after one ride burning all of the old gas I put in fresh gas with some Seafoam added in hopes it would do some passive cleaning of the carbs. Another 30-40 miles of riding with the Seafoamed gas didn't help. So I decided to pull the carbs and do a more mechanical cleaning/check. In the process if taking it apart I found a couple of little issues, worst of which was the aluminum baseplate on the UNI air filter had fallen off (!) and the petcock vacuum hose had hardened at the end where it connected to the petcock. Also there was a slight fuel leak at the tank petcock, hose clamps were loose. I figured these may have all come together to cause the running issues but I pulled the carbs and took the bowls off anyway. Carb bowls and jets were clean, I didn't bother checking the float level or float needles since it was all correct and nothing had changed.
When I put it all together, I screwed a bunch of stuff up. Well I put it together correctly and everything was golden but I accidentally left it on PRI for an hour and the float valves leaked, overflowed gas onto the ground and into the cylinders. I pulled the plugs and blew the fuel out, then the bike started and ran fine. Went for a ride with my dad, once it got warm and was off of choke it died at idle again and wouldn't start back up. I finally got it started on the side of the road and kept the choke on so it wouldn't die while I rode it home. As long as it's kept above 3K rpm it runs like a scalded cat. But it wants to die constantly if you take it off choke.
At this point, it starts perfectly with choke when it's cold and everything works as expected except I can't make it run below about 2500 rpm. If I adjust the throttle stop / idle speed sufficient to keep the idle above 2500 then it will run but if you know much about these carbs, you know that this is not actually an idle speed adjustment. It'll still eventually drop to "idle" and die no matter what. It's just cranking up the throttle stop will cause the idle to "hang" at higher revs and at least prevent it from dying while you are braking at a stop sign, but at a stop light you have to blip the throttle to keep it running and prevent it from actually idling.
I am no stranger to these carbs. Right now I am thinking maybe oil from the UNI filter has made its way into the idle air inlets, or maybe the deformity of the 30 year old airbox rubber boots (which is extreme...) might be blocking the idle air inlets. The pilot jets are definitely not blocked, I cleared them with a wire and there was no obstruction, and it runs at light throttle and middle revs with no problem. Pilot mixture is set at 2-1/2 turns out which is a good initial setting, but IIRC before I wound up with more like 2-1/4 turns out to make it idle perfectly but of course I can set this until I can get it to idle when warmed up. Should basically run with 2-1/2 turns out.
Anyway, I'm at my wit's end on this. So frustrated with this, I just have no more patience for it. Maybe one of you knows what this issue might be, and especially if you are local, you know I have a pub in my house... there's probably a couple of good beers in it if you wanted to stop by and help me sort this hands-on. I'll take whatever help I can get, from expert advice to turning a wrench.
This bike has maybe 5K on it since a top end rebuild and has been pretty much dialed in but fell to only occasional use after I got my Triumph a couple of years ago. I had just sorted a frustrating tuning issue in the summer before I had surgery and couldn't ride a couple of months and then I wrecked my Triumph and had my foot in a cast and couldn't ride a couple more months. Basically that means the bike was running perfectly in June when it was parked and then in late November when I got back on it, it had gone south. I always run ethanol-free fuel in it and even though there was no fuel stabilizer in it when it was parked, it at least not ruining its own o-rings with ethanol.
The engine is basically stock. Has a UNI air filter, shortened Yoshimura muffler and header wrap. I think it's currently jetted 125/40 with one washer on the needles. In June it ran perfectly.
OK, so when it came off hibernation it didn't want to idle. Everything started and ran ok but once it was warmed up and you turned the choke all the way off, it would die if it tried to idle. Also it wouldn't start unless I put it on PRI, and sometimes wouldn't run unless on PRI. I figured maybe the cabs were gummed or clogged up, and after one ride burning all of the old gas I put in fresh gas with some Seafoam added in hopes it would do some passive cleaning of the carbs. Another 30-40 miles of riding with the Seafoamed gas didn't help. So I decided to pull the carbs and do a more mechanical cleaning/check. In the process if taking it apart I found a couple of little issues, worst of which was the aluminum baseplate on the UNI air filter had fallen off (!) and the petcock vacuum hose had hardened at the end where it connected to the petcock. Also there was a slight fuel leak at the tank petcock, hose clamps were loose. I figured these may have all come together to cause the running issues but I pulled the carbs and took the bowls off anyway. Carb bowls and jets were clean, I didn't bother checking the float level or float needles since it was all correct and nothing had changed.
When I put it all together, I screwed a bunch of stuff up. Well I put it together correctly and everything was golden but I accidentally left it on PRI for an hour and the float valves leaked, overflowed gas onto the ground and into the cylinders. I pulled the plugs and blew the fuel out, then the bike started and ran fine. Went for a ride with my dad, once it got warm and was off of choke it died at idle again and wouldn't start back up. I finally got it started on the side of the road and kept the choke on so it wouldn't die while I rode it home. As long as it's kept above 3K rpm it runs like a scalded cat. But it wants to die constantly if you take it off choke.
At this point, it starts perfectly with choke when it's cold and everything works as expected except I can't make it run below about 2500 rpm. If I adjust the throttle stop / idle speed sufficient to keep the idle above 2500 then it will run but if you know much about these carbs, you know that this is not actually an idle speed adjustment. It'll still eventually drop to "idle" and die no matter what. It's just cranking up the throttle stop will cause the idle to "hang" at higher revs and at least prevent it from dying while you are braking at a stop sign, but at a stop light you have to blip the throttle to keep it running and prevent it from actually idling.
I am no stranger to these carbs. Right now I am thinking maybe oil from the UNI filter has made its way into the idle air inlets, or maybe the deformity of the 30 year old airbox rubber boots (which is extreme...) might be blocking the idle air inlets. The pilot jets are definitely not blocked, I cleared them with a wire and there was no obstruction, and it runs at light throttle and middle revs with no problem. Pilot mixture is set at 2-1/2 turns out which is a good initial setting, but IIRC before I wound up with more like 2-1/4 turns out to make it idle perfectly but of course I can set this until I can get it to idle when warmed up. Should basically run with 2-1/2 turns out.
Anyway, I'm at my wit's end on this. So frustrated with this, I just have no more patience for it. Maybe one of you knows what this issue might be, and especially if you are local, you know I have a pub in my house... there's probably a couple of good beers in it if you wanted to stop by and help me sort this hands-on. I'll take whatever help I can get, from expert advice to turning a wrench.
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