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Can anyone get the gremlin out of my Carbs?

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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I bought an '85 GS 550 EF (cali model) about a month ago. The guy I bought it from bought it from the original owner, who let it sit in the garage for some six years. Owner number two bought it, thinking he would restore it, but did not have the time. So here is where I come in, picking it up for under $300 from owner number two, thinking a night of carb work and I am off to the races (only a figure of speech with a 550). Well, I still cant get the thing to run right. I have torn down the carbs about 8 times (including letting them soak in cleaner over night twice), replaced everything in the carbs except the needles, needle jets, and the diaphrams (which look good), pulled off the plugs over the air mixture screws and fiddled with them, changed the air filter, adjusted the valve clearances, checked the spark, checked the compression, checked for vaccuum leaks. NOTHING!!! The bike should run well, if not perfect. I have the stock jetting according to the Clymer manual. I have a Dynojet kit coming monday; hopefully that will help, but ????? I can get it to start right up and idle with the choke on, but it will NEVER idle without the choke. If I open the throttle to bring the R's to 3500-4000 and then turn the choke off (with the motor warm) it dies immediatly. I have taken it around the block and it wont get past 6000RPM. It just surges violently. This should mean it is severely lean, but should it be this lean with stock jetting? I am about to go postal on this thing or throw in the towel. PLEASE HELP ME!!!!
 
Have you checked the ignition timing? After all you have done, it seems to me that this can only be an ignition problem. If the ignition timing is set too late, the engine won't idle, and that would explain the rev limit too.
Your bike probably has an electronic ignition. Perhaps you should have it checked by a professional.
 
timing vs carb idea

timing vs carb idea

Here is a little something I do, I think it accurately diagnosis some problems. With the bike running in park try to rev it up and hold it at like 8000 RPMs for a few seconds, if it holds there there probably is nothing wrong with your ignition timing or CDI box. Make sure your battery is charged, This can cause CDI ignition to do wierd things.
Other than that it sounds like some sort of carb problem, a good site for info and parts is www.motorcyclecarbs.com

Good Luck
 
Can anyone get the gremlin out of my Carbs?

The first thing that I check on a new old bike is the ignition (plugs, wires, timing, etc.) It is the easiest in that it involves less dismantling. So I will assume you have done that. The second is airfilter, airleaks, etc. You have done that. The third is to check the pilot air and mixture screws to ensure that they are at least somewhere close to suggested settings. Sounds like you have done that. The next is carb dismantle and cleaning. Before I soak I ensure that the idle circuit allows passage of air. I do this by fitting a piece of carb bowl overflow tubing or other small tubing over all opening (especially pillot jet and pilot jet carb body passages) and trying to blow air through with my mouth. If I can't here the breath blowing through, I assume there is varnish blocking the passages or jets. Soak and blow compressed air throough to blow out disolved varnish. Check with breath again. Still no air coming through I use an extremely small diameter wire and with extreme care (so as not to damage the jets) clean the remaining varnish out. Using wire to unplug jets and carb passages is usually not recommended but if the alternative is trashing the carbs it is worth trying. Soaking is OK for softening the varnish but unless you ensure that the passage is clear it does no good. Your ploblem sound very much to me like plugged idle circuit. If the idle circuit is plugged it will also run lean at higher RPM because both the idle circuit and the main jet are used at high RPM.

I have a CB550 Honda that had not been driven for four years when I got it. It would not idle exept with the choke pulled all the way out. The idle jets were so varnished up that I had to take an ultra light gauge high E guitar string, bend it into a crank shape and crank it into the jets to get the varnish out even after soaking. The ultra light gauge high E guitar string was the only thing small enough and stiff enough to get into the jet without damaging it. After cleaning in this way the bike starts and idle very well. Varnish is and idle bikes worst enemy and soaking alone just doesn't do it. Good Luck!

Junkman
 
I had a similar problem (see http://www.thegsresources.com/_forum/viewtopic.php?t=5008&highlight= - second to last response).
So, if you try restricting the amount of air making its way ito the carbs the way I did (even though you already have an air filter), does it get better? If so, that probably is evidence of an air leak somewhere. It's a low-effort test, so it's worth trying. These CV carbs are extremely sensitive to improper air flow or air leaks.
Even after I got an air filter, I had some minor leaks by the seal between the air box lid and the air box itself. After I got all my air flow and/or air leak problems worked out, the bike ran near perfect.
It took me days to sort my problem out (I also tore down my carbs several times).
Let us know, keep at it and good luck.
 
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