GS850 too rich

[gssuzukixxx]

Had the '79 GS850 running really good for a little while then it started to miss when cold. Only after it was completely warmed up and run at high RPMs would it clear up and run smoothly. Took the plugs out and they were all black and sooty. Let it cool down and started it up and clipped my timing light onto each ignition wire. Sparking was hit and miss and a couple of the cylinders. Bought 4 new plugs and put them in. Started up cold and every cylinder sparking regularly and all cylinder running smooth.

Now I am figuring it is running too rich and fouling the plugs. I live in Calgary which is about 4000' above sea level and ever vehicle I have tuned has needed to be leaned out a bit to run best. I am thinking of lowering each needle by 1 notch and trying that. Is 1 notch a huge change?

What do you guys think?

Brian

 

[gssuzukixxx]

Also, I took out a throttle slide...the needle has 5DL36 stamped on it.

Any thought on this?

 

[tkent02]

That's the needle for a GS1000, I thought the 750 used a different one?
Maybe you have 1000 carbs?
Where is the idle adjuster located, on top or on the bottom?
One notch is a fairly large change, you can go half steps with the use of small washers..
How are the fuel and the air screws set?

Stock intake and exhaust?

 

[gssuzukixxx]

Thanks for the response. This is a '79 GS850. The idle fuel screw is located on the bottom. Idle air is turned out 1 turn.

The clip is in the second notch from the top, there is a thin nylon washer between it and the spring and then there is a thicker nylon washer on top.

 

[tkent02]

Sorry, brain fart, the '79 850s and the 750s had the same jets, everything identical.

I meant the idle speed screw, the big one that adjusts the throttles on all four together. It goes under on the 1000 carbs, on top of the 750/850 carbs.

Fuel screws underneath, something like 5/8 or 3/4 turn out, the air screws about twice that is a good starting point.

 

[Spyderman]

hey brian if you need info give me a call i'm off wed and thurs this week

 

[gssuzukixxx]

That idle screw is on the top.

According to BassCliff's carb spec chart 5DL36 is stock for a '79 GS850. With the clip second notch from the top someone has already tried to lean it a bit. The clip is normally in the middle notch right.

I guess I could look at the needle jets which will mean taking the carbs off the bike once again.

When the plugs are not fouled the bike runs nice. Another thought would be to just put in hotter spark plugs that might keep clean.

Brian

 

[tkent02]

No, that band aid never works very well.
Tune it right.
Again, where are the pilot fuel screws set? 5/8 or 3/4 out from LIGHTLY seated?
Best to look through the venturi as you screw them in, when you see the tips poke up unto the venturi stop.
If you seat them very hard at all the tips break off and get stuck.
One turn out on the air screws is probably not enough, causing richness at low throttle openings.
OK, so you have the right carbs. They just need to be set up right.

Don't pull the needle jets out, they don't go back in very well, there's no reason to.
They are pressed into the carb body at the factory, once they are knocked out you are screwed.

 

[gssuzukixxx]

Hey Jon,

Good to hear from you. As you can see I am trying to sort out the old 850. Seems to be running too rich so that it fouls the plugs. BTW the 750 is running awsomely.

Could it be that the idle air screw is off enough to cause this? I have never adjusted the idle fuels screws because I thought they were set at the factory and not to be messed with.

Brian

 

[SqDancerLynn1]

Before you change anything make sure you have the proper 12 volts at the coils (with the points blocked open) At 4K ft you may need to put in a smaller main jet

 

[49er]

Because you are running at 4000ft, you will need to lean the idle circuit, the needle position and even the main jet.

The stock settings for the '79 VM26SS carbs at sea level are:

Pilots #15
Needles 5DL36-2
Mains 95 -102

Pilot fuel screws 5/8 to 7/8 turn off the seat.
Pilot air screws 1.5 to 2 turns off the seat.

First things first. Have you checked the condition of your air cleaner/filter. It needs to be clean and lightly oiled. The needles are always set in the 2nd clip position, from the factory.

IMO, because of your altitude, you need your fuel screws around 5/8 off the seat. Your air screws around 1+1/2 - 2 turns + off the seat. The needles in the 3rd clip position. If this proves to be too lean, shim them with a .016" -.020" shim on top of the 2nd clip position. Make sure your mains are in the 95 region.

Don't fit hotter plugs unless you are prepared to baby it everywhere at lower rpm's. As said above, fix the cause, don't apply bandages.