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83 GS550L stalls on idle AFTER running @ mid-range

  • Thread starter Thread starter notzaar
  • Start date Start date
N

notzaar

Guest
Hi guys and gals, I hope you can help me with a strange issue. I did a search but couldn't find anything on this specific problem. It's a little complicated so I'll try to explain best I can.

Bike is 1983 GS550L, bought used (recently) with ~22k miles. I'm a motorcycle noob so maybe I bought a clunker without realizing it, but it was fairly inexpensive and performed well on the short low-speed test-ride I did.

Here is the deal:
1. The bike starts up reasonable fine, needs full choke to start cold and then will run without choke after a minute or two. Performs beautifully in low-speed town riding (max RPM 2-3k)

2. When I get out to the highway, I keep it at mid-range, around 4-5k RPM. It works great, no weird sounds or vibrations that I can hear/feel through the full-face helmet.

The problem:
After running at mid range RPM for a while (say 5-10 minutes), if I try to stop the engine will just die as soon as RPM start to drop. Then it behaves as though the engine is completely cold. It will not start without full choke and even a little bit of throttle. It takes about 30 seconds to get operational again at low RPMs, and even then it will sometimes stall at idle all the way home.

I am going to do a full carb rebuild soon (still need to order o rings and new gaskets just in case), but I'm wondering if anybody can tell me what is going on here. It almost seems to me like the carbs get stuck in "mid-range mode", maybe the slide can't come back down? I'm not very mechanically knowledgeable yet, so that's probably not correct.

I've tried riding with the petcock in "prime", but the problem will eventually rear its ugly head, although not until after 1-2 stops from mid-range. I've also liberally applied Seafoam into the gas tank in a desperate attemp to do a quick-fix, but it doesn't help.
 
You already know the problem. It needs a complete cleaning and rebuild with fresh o-rings. Cliff will be along shortly with his big bag of tricks and you will find the tutorial for the complete procedure.

Over a surprisingly short period of time gas can go off and turn into a varnish that can clog jets and passages. In addition, rust and junk from the tank often gets in there as well and can add to the problem. It may be that your primary carb circuits are clean but something is gumming the midrange.

While Seafoam is good and can sometimes alleviate the issues, the only sure fix is a through cleaning and rebuild. Just about every old bike I have ever touched has needed it.

Its not hard and make take a while the first time but from then on it will be a lot easier and quicker. Give it a go.

Welcome aboard by the way.

Cheers,
spyug
 
Thanks for the quick replies. I have seen Cliff's website in preparation for this carb rebuild. Previously I've only cleaned scooter carbs, so this should prove more challenging.
As far as fuel starvation goes, I've taken it on the interstate and driven it for up to 20 miles without any problems. The issue only manifests after I start to slow back down to city speeds.
 
With the bike warm set the idle speed to 1200 rpm.
Toss in an amount of in tank carb cleaner as per the instructions of the bottle and drive the **** outta it.

You idle may be set too low and and your idle jets may be a bit gummed up.
 
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