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78 GS550 needs less air

  • Thread starter Thread starter rgierer
  • Start date Start date
R

rgierer

Guest
This is a 78 550 I have had for about 18 months and never gotten quite right. It has plates and insurance but the original carbs, even after a thorough cleaning caused me nothing but grief and I went to a set of carbs from AOD, I put o-rings in and she fires right up, without spilling gas anywhere. (this in itself is cause for celebration)

It won't run without choke. I pulled air filter, stuck rags in the box and she ran great without choke. So I oiled up the filter and went through tightening the airbox top to bottom and it continues to get too much air. Only time it runs without choke is if I block vent on airbox.

There is no seal on airbox on metal to metal connection.

I put air and fuel screws back in carbs exactly as they came out.

If I was going to adjust my airscrews to allow for less air would I turn them in or out?

Guidance, counsel or sarcastic remarks welcome.

FYI The bike had been sitting for 14 years when I got it.
 
update

update

I went back at the 550 this morning and found another airbox (the front portion) and decided to switch them in case the other on had a crack some place. I found 2 things.
1) No seal on the first airbox between the plastic and metal portions.
2) the foam in the airfilter is dry rotted to the point that it doesn't hold oil. All of the oil had settled to the bottom one inch of the airfilter. I am no expert but I think it should be throughout the foam.

So next weekend I will replace the foam. I assume any similar size and weight foam will do and then I will try it again.

rg
 
rgierer said:
it continues to get too much air.
There is no seal on airbox on metal to metal connection.
FYI The bike had been sitting for 14 years when I got it.
Click to expand...

I'll take a poke at this.
Don't try cutting down the air. Yes, the airbox is allowing more air than normal but you're not getting enough fuel, even if the air box is good.
I don't know what you're saying about the metal to metal connection regarding the airbox. You should have rubber boots between the carbs and box, and a rubber boot to join the box and filter housing.
The VM carb equipped bikes will run lean, but not as bad as you're experiencing simply because of a "leaking" air box. There's more to what's happening here.
(By the way, just looked back and saw that your filter is shot and that helps make sense.)
If you want it to run correctly, you'll have to replace any missing rubbers mentioned above with good ones. Then replace the filter with a NEW filter. DON'T make a home repair with some foam that could restrict flow or deteriorate after time. You won't be happy with it.
Next, I think you have pilot circuit/vacuum synch problems because your problem is at start up. The pilot fuel screws underneath should be about 1 1/4 turns out for starters from LIGHTLY seated. Where are yours at? Careful of tight screws.
Next, where are the side air screws set at? Try 1 1/2 turns out initially. Careful of tight screws. If it starts up and holds an idle, adjust the idle to 1,100 rpm and set the side air screws using the highest rpm method. Test.
If you still have the problem, I suggest a GOOD bench synch at least. Test. If you still have the problem, I suggest cleaning the pilot circuit passages. Also be sure you don't have any broken tips from the pilot fuel screws stuck in the carb bodies. Might as well verify the float levels when you have things apart.
 
Thank you for your thoughtful guidance. Screws are set as they were when I cleaned and replaced o-rings. (Within 1/4 turn of what you referenced)

I will spend time on the bench synch as you suggested.

I will also spring for the new filter

RG
 
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