adjusting mixture screws does nothing.

[jonandjones]

I am working on adjusting the air mixture screws. Doing the dead cylinder method, Anyway I turn the mix screw makes no difference in idle. I am assuming something is clogged in the pilot curcuit? Or what else could it be?

 

[retiredgentleman]

Don't try to do this at 1200 rpm. You need to lower the rpm with the throttle speed screw, down to just above a stall, perhaps 300 to 500 rpm. This lower rpm has the by-pass holes blocked off by the butterflys. With the by-pass holes providing mixture its impossible to detect any change from the mixture screw.

The rpm change as you tune the mixture screw is subtle, so you have to listen carefully.

 

[jonandjones]

I turned the rpms down till it just about won't run. The change is suddle I guess I was expecting a sudden change like the rpms going up cause then there is talk about adjusting it back down with the idle screw.

 

[grizld1]

Go to the Tech section, click the link for the Carb Guide, and read. Nonresponse to the mixture screw is often caused by incorrect pilot jet type, incorrect pilot jet size, or defective parts or adjustment of float and/or float valve.