Another way to check lean vs. rich on an engine is to hold the plane level. Run the throttle up to get full speed on the engine. Then raise the nose up to between 60 to 90 degrees above horizontal.

If the engine drops rpm or dies, it is too lean. Open the high speed needle 3 or 4 clicks and try agein.

On the other hand, if the engine speeds up when you do this, it is set on the rich side.

I try to set my engines so they don't change rpm when help up at this angle, then open the high speed needle a click richer.

I always operate on the principle that rich engines last a lot longer than lean engines.

Note, if you try this same test, but lower the nose of the plane, then if it slows down, it is on the rich side, if it speeds up, it is on the lean side.

Hope that this info is helpful.