Question on Mixture Screw
 

The question which direction do you turn the mixture screw to enrichen the mixture on an 81 sc? Waynes book says clockwise but I have tried that several times with no sucess. WHen I turn it counter clockwise you car hear the engine slow down which means to me that it is enrichening the mixture.

The whole reason for this is the car was missing and sputtering and I wanted to eliminate that by setting the correct mixture and check everything out in the CIS. everything is operating correctly so it must be mixture. ANy ideas?

Ben
77 911 3.0
75 914-6 2.7

Before setting the mixture, everything else has to be done. Valves, Plugs, Timing...........Mixture adjustment is Clockwise-rich. But, it takes very little to make a difference. Even a fraction of a turn is effective. It is a combination between mix adjust and idle speed adjust (The big spring-loaded screw) Don't leave the Allen key inside when reving. Missing and sputtering could be a vacuum leak somewhere.

Easy way to remember, "lean out". In other words turn the screw out (CCW) to lean it out.
I've heard it said that you are supposed to go from lean to rich when adjusting, I don't know why. That would mean that you would have to lean it out past the desired point then go back to a richer point. Doesn't make sense to me and I've never noticed a difference doing it that way.

When making adjustments turn it a small amount then blip the throttle after removing the allen wrench. Then adjust idle speed as required, then test to see if that's where you want it.

to my understanding it is because the screw is spring loaded.. thus the spring will be properly seated.........Ron

That's usually an ignition problem which I would address before moving on to mixture.

Joe

Ignition is all brand new and checks fine the strange thing is the all the problems are gone noe that I turned the screw counter clockwise> I wonder if The screw was turned to far clockwise and was out of adjustment. I think I am in the correct operating range but I have to read the plugs. Is it possible to rotate to far clockwise? any ideas

Ben
77 911 3.0
75 914-6 2.7

Correct info above. I was told once, left=lean ... right=rich.

My own mix adjust screw is not indexed and I have seen other people on this board stating that they don't feel any click when adjusting. Without taking things apart, I don't know why some people have the index and others do not. You can definately tell when you are getting lean: Go SLOWLY ccw untill the RPM drops (lean) Now go SLOWLY cw and you'll notice improved idling. Continue cw (rich) until again the idle becomes irregular. Select a position inbetween the two. Maintain the idle RPM (950) while you are adjusting mix. It takes very little of a turn to have a noticable effect on mix adjust. I do the above without a CO meter and it works for me.

Gunter that makes sense that is what I was shooting for but the strnge thing is when working with carbs as rpm decreases the richer it is I guess CIS is different. What color are your spark plugs using this method?

Ben
77 911 3.0
75 914-6 2.7

I assume that we are talking about CIS, not carbs. The plugs are Bosch W5DC, standard for an '80 SC and they burn light brown.