This is the area of the head to attach the tape measure to for measuring the specs on the new exhaust for the Ducar 212
Stroke gauge I designed for a fast check.  The predator has made this gauge a valuable tool to have in your tech box
Picture
.031 no go for the air bleeds
This was a ride I took in my first outing after 20 years of not racing.  Funny thing is, the last ride 20 years ago sent me to the hospital with the same kart.  Why I got into this thing again is beyond me.  Two artificial knees, 6 bars in my back and a right foot lis frank sprain.  My wife told me if I do it again I will be sleeping in the garage with it.  The temptation to ride it again is getting worst!!!
Picture
multiple use plugs for internal check points of the Ruxing, Hayui, and Tillotson pk-1
checking the distance of the e-tube to the .750 step.Tool on left may not push plug on right out of the bore.
Recommended method of using tool from last picture.  Hold down on solid base and try to slide carb up and down.  If carb does not move it is legal.
 Picture
This is an example of using the tool to identify that there is a portion of the machined venturi showing in front of the gauge.  I highlighted the area in red so as to demonstrate there is venturi visible.  The 2020 rules state there must be a visible portion of the venturi in front of the gauge.
This may cause a necessity for a magnifying If you look real close you will see there is a highly machined area of the venturi ahead of the tool that is slid over the e-tube.  The rule says there must be a portion of the highly machined venturi ahead of the e-tube.  Some carbs might need to have the gauge tipped upward or downward to get the venturi to come into view which is permitted.  The use of a magnifying lens may sometimes be called for. 
Go to Youtube to see video. https://youtu.be/8JmS606QzTo