Suffolk Punch Zenith carb adjustments

[Ross365]

I have an old Suffolk Punch petrol lawn mower which has a Zenith carb, model 13 TCA-2, as pictured. Something I’ve never quite understood about this carb is that it has two screws that control the mixture. On top, there is the air-enrichment screw and on the side is the mixture screw - see pic.​

I’ve never managed to find any info on how to adjust these screws other than that the enrichment screw should be ¾ of a turn off its seat and the mixture screw ¾ to 1 turn off its seat.​

I wonder if anyone knows anything more about how best to set these up?​

Thanks​

Ross​

 

[Robotstar5]

The top one is the idle speed mixture and the side one is the main running mixture.

 

[slim_boy_fat]

Wot 'e said ^^

 

[Ross365]

Many thanks for that, but is there a procedure to get them optimised other than the arbitrary settings for backing off the screws?

I had to strip down the carb as the float valve was not shutting off, and that all went well and I ultrasonically cleaned it and then I set it up with the nominal screw settings, which worked. Tickover is fine, but the engine seems a bit down on power and isn't pulling as well as it used to. Haven't looked at the plug yet to see what that looks like.