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Carburetor "spitting"

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

Anonymous

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Ok, here is the problem, I need some advice.

I have a 78 GS1000, very low miles. When I purchased it it would not start without starting fluid and would only stay running when giving it gas and would not idle. The previous owner had someone work on it. He said they had to sync the carbs but I am not sure that this was done accurately. I concerned that whoever worked on this previously did not know what they were doing and fiddled with the mixture.

Now I have rebuild the carbs and now the bike fires up easily when started. It seems to run ok, however at idle speed I am getting a "spitting" through the carbs. It has difficulty idling at 1000-1100 rpms as recommended by the manual. I can raise the idle above 2000 rpms and the that seems to improve it. When removing the spark plugs I find them black and sooting. What is the next course of action to resolve this.

Thanks in advance for the help
 
Hmmm..super rich on the carb that is spitting. I used to have the same problem when my main jets were too big for the exhaust I was running.
Have any mods been done to the bike?

Dm of mD
 
Hi. I have a '79 GS1000. The "spitting" is a lean condition.
I'll assume you did a good cleaning and used compressed air so the fuel passages are clear AND the o-rings are in good condition. The floats should be set at about .94", the middle of their spec' range.
If the intake/exhaust is stock AND the stock air box still has its lid, the pilot screws (underneath) should be set out about 1 1/4 turns. This is just a ballpark guess. The factory sets them anywhere from 3/4 to 1 1/2 turns out. THIS ONLY APPLIES IF YOU HAVE THE SHARP-TIPPED SCREWS. To get them right, you need to take plug reads and tinker with them. They are for fine tuning the pilot circuit and are commonly set at different points to allow for differences in each cylinder. You may find your final settings are: 1 1/4, 1, 1 1/8, 1 1/2 as an example. Check out my topic about fuel and mixture screws in the "tips & tricks" section for more info.
Next, your side air screws should be set for the highest rpm possible and then the idle re-set to 1,100 rpm with the idle screwknob. Put the bike on its centerstand and warm it up first. Turn two air screws at a time in 1/4 to 1/2 turn increments to more easily hear the rpm's max'. Fine tune these two and then do the other two. When all four are set, re-set the idle with the idle screwknob.
Make sure the o-rings in the rubber manifolds are in good condition (no cracks or hardening) and greased with some hi-temp' bearing grease. Torque them to 6 ft/lb. Make sure the carb clamps on each side are tight.
A good carb synch using a vacuum tool is important with these carbs. Make sure the plugs are gapped and the air filter is clean.
If you still have the spitting let us know.
You did'nt say what throttle position(s) gave you the rich black plugs, but the above info may fix that problem too.
 
78 GS100 here.

As Keith said. If the carbs have been run out of synch for a while you may find it needs a good run to clean it out before getting the idle mixture right. Mine recently had a plug cap problem that caused to bike to carbon up a bit, it nows runs a lot better down low after proper carb synch and riding it a while to clean it out.

Also make sure the fuel is fresh, as old fuel can couse problems.
 
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