I changed the spark plugs the other day and noticed they were rather dark and had small buildups. Not enough to do damage, but enough to say I'm running a little rich. I found the screws but not sure how much or which way to turn them. Logic tells me I should screw them in (screw in like a tape makes gap inside smaller and less fuel flow.) So, How far should I go? (Keeping in mind its not running rich enough to damage the plugs.) And am I right about the direction? Thanks people.

I changed the spark plugs the other day and noticed they were rather dark and had small buildups. Not enough to do damage, but enough to say I'm running a little rich. I found the screws but not sure how much or which way to turn them. Logic tells me I should screw them in (screw in like a tape makes gap inside smaller and less fuel flow.) So, How far should I go? (Keeping in mind its not running rich enough to damage the plugs.) And am I right about the direction? Thanks people.

 

The screw is basicly a small air port and uses a needle to open or block a hole accordingly. More air is lean and less air means it has to suck more fuel and therefor rich. turning in (clockwise) lessens the air flow and richens so you should turn counterclockwise.

Emissions-era carbs tend to have the "reverse"-mixture screws that galopagus described. The bad news is that just effects the idle mixture.

 

Make sure that the carb(s?) is clean (especially the air bleeds in the air horn) and that the float-vavle is properly set. Also, is this a (are these?) feedback carb(s)? Without the feedback working, the mixture will be slightly rich.

Yikes so now I'm confused, which way to turn to lean? How do i find out which carb I have?

Sorry, but I can't help.

I'm just going to stick with, it works, leave it alone.

It would be good to find a manual for the carbies I got, but how to find out what carb they are is beond me.

Well seems like my carb needs rebuilt, had it checked and i'm not getting enough fuel in there, its running lean either way I turn the mixture screw, doesnt change much. Very weird. Not sure if he's right or wat but he showed me on his emissions computer, he turned the screw from all the way left to all the way right and the HC's were really high either way.

remember that the screw is most likely just an idle mixture screw.