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Hello All,
I just put a thread in the GS owners section to introduce myself. I have been doing some reading on the site, but am wondering if anybody has any other suggestions for me while working on my 1984 GS550ES. Here goes my story.
At the end of last year my bike quite running one day when I was about a mile from home. I pushed it home and left it sit a few hours and it started again, but wasn’t running right. After a few minutes it died again with no spark. Anyway, it ended up being a bad signal generator coil. I ebayed a used one, checked the resistance measurements which checked good, installed it and my bike ran again with new plugs. However when driving it, it was hesitating under moderated loads. It would run WOT pretty good, idle good, and cruise pretty good, but hesitated and missed mostly in 5th and 6th gear when accelerating from 1/8 throttle. Then I noticed the airbox drain would drip about a half-dollar sized amount of fuel on the ground when I parked it on the side stand. After the initial drips there was nothing else if left over night on the ON or RES petcock position.
So I removed the BSW carbs to clean them and check things out. I also removed the new plugs and inspected them. The two LH side plugs (LH carb) had a slight black ring around the base whereas the two RH plugs (RH carb) were clean and looked good. Also, in the process I found out the airbox had warped and wasn’t sealing against the air filter anymore. The carbs had some contamination in them. I diassemmbled and cleaned the carbs with spray brake cleaner and blew out all the passages with compressed air. I did not remove the fuel screws because I have done that before on other GS’s and it was a pain. My idle quality is also good so I didn’t think they would be a problem. I did not soak the carbs because I didn’t want to disassemble the rack and have the crossover tube o-ring leak again (I replaced them a few years back). I checked the needle and seat seal, and the o-ring by hooking up a vacuum gauge to the fuel inlet barb and checking the leakdown with the needles just sitting in the seats with the bottom of the carbs up. The RH side had a small amount of leakdown – about 2-3 inHG in a minute. If you put light pressure on the needle it didn’t leak at all. Other carbs where I found the needles would cause running problems usually leak down completely within seconds. The LH needle was good with no leakdown. These needles were new Suzuki parts about 5 years ago.
So I double check the float settings and adjusted the LH side a little so that they were both in the middle of the Clymer manual tolerance which I think was 20.5 mm without the gasket. I checked the slide diaphragms and reassembled the carbs. There was a little bit of varnish in the LH choke plunger orifice that I cleaned with brake cleaner and Yamaha carb cleaner as best I could. I checked function of the choke plungers both sides and they seemed to be fine. So back on the carbs went. I added foam to the airfilter so it sealed and away I went. I also checked the ignition system and coil connections and put dielectric grease on the terminals.
Well, my fuel mileage is down to about 38 MPG from the usual 42 MPG. Plus it still drips some fuel from the airbox drain only just after I shut it off. Sometimes a few drops, sometimes a three inch circle worth. Yesterday when I got home from work, I left the bike running on the center stand for about five minutes and no fuel dripped. I left it on the center stand for about 15 minutes and not one drop. I put it on the side stand and about 5 drops fell. I wonder if the fuel is blow-back from the carb or is it from to high of float level/leakage. It does run better after the carb cleaning, but it still misses during moderate acceleration mostly in 5th and 6th gear under load. I am trying to get through the information posted here, but there is a lot of stuff. Here is a list of things I have thought about, but haven’t done yet.
- I haven’t check compression or done a leakdown test yet.
- Need to check plugs again and see what they look like.
- I haven’t changed the intake o-rings.
- When I changed the needles, I think I reused the o-rings. However I was thinking my vacuum check would prove they were OK.
- The petcock does not let fuel run in the ON or RES position – only the prime.
- No fuel drips from the petcock pulse line plug when the tank is on the bench and hoses are disconnected.
- I haven’t checked timing since the signal generator assy change because it isn’t easily adjustable, but I should probably do this.
- I haven’t tried to take a “live” reading on fuel level, but I could probably do this fairly easily using the float bowl drain screw holes.
- I wonder if the LH side choke plunger isn’t sealing completely. Does anybody know if this is a common problem? What is the best way to test this? I might just switch the plungers from side to side and see what happens. Would this cause the carbs to spray back gas into the airbox??
It seems like it almost has to be a fuel level problems, but I don’t know what else to do since the needles didn’t leak down. The petcock and diaphragm seem to be good since it doesn’t leak with the hoses disconnect and the tank pretty full of fuel.
Anybody have any suggestions or see that I am missing something?
Thanks much,
Ryan Zahn
p.s. sorry for the typos........... :?
I just put a thread in the GS owners section to introduce myself. I have been doing some reading on the site, but am wondering if anybody has any other suggestions for me while working on my 1984 GS550ES. Here goes my story.
At the end of last year my bike quite running one day when I was about a mile from home. I pushed it home and left it sit a few hours and it started again, but wasn’t running right. After a few minutes it died again with no spark. Anyway, it ended up being a bad signal generator coil. I ebayed a used one, checked the resistance measurements which checked good, installed it and my bike ran again with new plugs. However when driving it, it was hesitating under moderated loads. It would run WOT pretty good, idle good, and cruise pretty good, but hesitated and missed mostly in 5th and 6th gear when accelerating from 1/8 throttle. Then I noticed the airbox drain would drip about a half-dollar sized amount of fuel on the ground when I parked it on the side stand. After the initial drips there was nothing else if left over night on the ON or RES petcock position.
So I removed the BSW carbs to clean them and check things out. I also removed the new plugs and inspected them. The two LH side plugs (LH carb) had a slight black ring around the base whereas the two RH plugs (RH carb) were clean and looked good. Also, in the process I found out the airbox had warped and wasn’t sealing against the air filter anymore. The carbs had some contamination in them. I diassemmbled and cleaned the carbs with spray brake cleaner and blew out all the passages with compressed air. I did not remove the fuel screws because I have done that before on other GS’s and it was a pain. My idle quality is also good so I didn’t think they would be a problem. I did not soak the carbs because I didn’t want to disassemble the rack and have the crossover tube o-ring leak again (I replaced them a few years back). I checked the needle and seat seal, and the o-ring by hooking up a vacuum gauge to the fuel inlet barb and checking the leakdown with the needles just sitting in the seats with the bottom of the carbs up. The RH side had a small amount of leakdown – about 2-3 inHG in a minute. If you put light pressure on the needle it didn’t leak at all. Other carbs where I found the needles would cause running problems usually leak down completely within seconds. The LH needle was good with no leakdown. These needles were new Suzuki parts about 5 years ago.
So I double check the float settings and adjusted the LH side a little so that they were both in the middle of the Clymer manual tolerance which I think was 20.5 mm without the gasket. I checked the slide diaphragms and reassembled the carbs. There was a little bit of varnish in the LH choke plunger orifice that I cleaned with brake cleaner and Yamaha carb cleaner as best I could. I checked function of the choke plungers both sides and they seemed to be fine. So back on the carbs went. I added foam to the airfilter so it sealed and away I went. I also checked the ignition system and coil connections and put dielectric grease on the terminals.
Well, my fuel mileage is down to about 38 MPG from the usual 42 MPG. Plus it still drips some fuel from the airbox drain only just after I shut it off. Sometimes a few drops, sometimes a three inch circle worth. Yesterday when I got home from work, I left the bike running on the center stand for about five minutes and no fuel dripped. I left it on the center stand for about 15 minutes and not one drop. I put it on the side stand and about 5 drops fell. I wonder if the fuel is blow-back from the carb or is it from to high of float level/leakage. It does run better after the carb cleaning, but it still misses during moderate acceleration mostly in 5th and 6th gear under load. I am trying to get through the information posted here, but there is a lot of stuff. Here is a list of things I have thought about, but haven’t done yet.
- I haven’t check compression or done a leakdown test yet.
- Need to check plugs again and see what they look like.
- I haven’t changed the intake o-rings.
- When I changed the needles, I think I reused the o-rings. However I was thinking my vacuum check would prove they were OK.
- The petcock does not let fuel run in the ON or RES position – only the prime.
- No fuel drips from the petcock pulse line plug when the tank is on the bench and hoses are disconnected.
- I haven’t checked timing since the signal generator assy change because it isn’t easily adjustable, but I should probably do this.
- I haven’t tried to take a “live” reading on fuel level, but I could probably do this fairly easily using the float bowl drain screw holes.
- I wonder if the LH side choke plunger isn’t sealing completely. Does anybody know if this is a common problem? What is the best way to test this? I might just switch the plungers from side to side and see what happens. Would this cause the carbs to spray back gas into the airbox??
It seems like it almost has to be a fuel level problems, but I don’t know what else to do since the needles didn’t leak down. The petcock and diaphragm seem to be good since it doesn’t leak with the hoses disconnect and the tank pretty full of fuel.
Anybody have any suggestions or see that I am missing something?
Thanks much,
Ryan Zahn
p.s. sorry for the typos........... :?
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