GS550E Carb problems?

[new_gser]

I have a 1986 GS550E that I had posted for sale. There did not seem to be much interest in it so I pulled down the post and decided to fix it and keep it for myself. I just replaced the carb boots between the carb and the engine, the boots between the carb and airbox are fine. When I started it I held the choke about halfway for about 45 seconds. I let it warm up for 5 to 10 minutes and adjusted the idle to about 1200 RPM's. (If I go much lower the bike starts to run rough and stall) I took it for a 10 minute ride and it ran great. I stopped at a store and when I came out and restarted the bike, the idle was about 800 rpm's and I could not keep it running. I had to use the throttle with the clutch pulled in to keep it running. I got it home this way, but every time I had to shift it would stall because I had to release the throttle. (clutch starting at 60mph is NOT a good idea, but standing up a 22 year old bike was kind of cool!!) I put about 250 miles on it before I replaced the boots. It actually ran better with the torn boots on it. Any ideas?

[Skyboy8950]

You should check your mixture screws. You may have made it too rich to compensate for the torn boots. Once you get those dialed in, take it for a spin, let it get warm, then adjust the idle screw to where you want it.

[MelodicMetalGod]

Welcome new_gser!!!

Sounds very much like my bike when I first got it. The main issue turned out to the be the carbs - they needed a good cleaning, particularly the pilot circuit. There are certainly other possible causes, but if you haven't cleaned the carbs, check 'em out.

Best of luck!

[new_gser]

I cleaned the carbs last year when I started to rebuild it and I have not touched the mixture screws, but the previous owner may have so I will check it out. Also, when I had torn boots after running for 10-15 minutes the rpm's would be up to about 4500 at idle, but now that I replaced the boots the rpm's drop to around 800 or lower after running for 10-15 minutes. Could I have a problem with the filter or line coming from the airbox?

[Nessism]

I cleaned the carbs last year when I started to rebuild it and I have not touched the mixture screws, but the previous owner may have so I will check it out. Also, when I had torn boots after running for 10-15 minutes the rpm's would be up to about 4500 at idle, but now that I replaced the boots the rpm's drop to around 800 or lower after running for 10-15 minutes. Could I have a problem with the filter or line coming from the airbox?

How can you clean the carbs but not touch the mixture screw? Sounds like you need to pull the carbs and clean them properly by taking them apart and replacing the old and hard o-rings.

[doctorgonzo]

I'll secon "proper" carb cleraning, and idle drop when warm indicates rich if I'm not mistaken.

[new_gser]

O.K. Thanks for the info. I will check this out as soon as I can. Is there a starting point for the mixture screw? Example.. Turn in all the way and back out 3 turns or whatever it may be?

[doctorgonzo]

O.K. Thanks for the info. I will check this out as soon as I can. Is there a starting point for the mixture screw? Example.. Turn in all the way and back out 3 turns or whatever it may be?

I'd start at 2, maybe 2.5. Can really vary between bikes, so hard to say. If it's stock, the factory setting (which is likely a tad lean) is in the manual.

[MelodicMetalGod]

O.K. Thanks for the info. I will check this out as soon as I can. Is there a starting point for the mixture screw? Example.. Turn in all the way and back out 3 turns or whatever it may be?

I've seen recommendations from 1.5 to 3.5 turns out. Pick your poison and tune the carbs via highest idle method, etc. Each bike is different, so you'll need to tune it for best optimum results.

Best of luck!

[MelodicMetalGod]

I'd start at 2, maybe 2.5. Can really vary between bikes, so hard to say. If it's stock, the factory setting (which is likely a tad lean) is in the manual.

Are you certain that there is a spec in the manual on this? I thought that the pilot screws were essentially ignored since the were sealed from the factory and not supposed to be user serviceable/adjustable.

[new_gser]

Where are the mixture screws on the carb? I looked and I am not sure where they are. (a pic would be helpful) I have never had to adjust them on previous bikes I have owned. This is my first project bike. Also, on one of the other posts there is a shop manual for an 83 GS550E. Can this manual also be used for an 86?

[new_gser]

Well, I had the day off today and a friend of mine and helped me check the mixture screw. Turns out 3 of them were 2 turns out and 1 was 1 turn out. Started them out at 2 1/2 turns each and she ran better so we adjusted them to 3 turns out each and it is running and idling fine. Took it for a short ride and I was very happy with the performance. Now I just have to look into my charging problem. Thanks for all the good info.

[MelodicMetalGod]

Where are the mixture screws on the carb? I looked and I am not sure where they are. (a pic would be helpful) I have never had to adjust them on previous bikes I have owned. This is my first project bike. Also, on one of the other posts there is a shop manual for an 83 GS550E. Can this manual also be used for an 86?

The pilot screws (a.k.a. mix screws) are sealed from the factory and not visible until you drill out the seal (a metal plug) above each of the pilot screws. They are located on either side of the choke ports on the front of each carb - see the pic below:

The 83 manual is appropriate and an excellent reference for the 83-86 models. However, it is an 83 version, therefore any slight changes made to subsequent years (not many) will vary from the manual. I've used it for my 85 and I haven't had any issues yet.