Lean yes...

The PTS also has a couple of basic problems... you are experiencing one.


The low end needle will "walk" as you advance and retard the throttle causing the tuning to change in flight. This is more pronounced once the engine warms up.


I've seen this with every PTS P-51 I've owned ( three ) and with those brought by others out to our field ( five ).

My first solution to this was to insert a cut piece of an exhaust deflector tube, to fit over the LS needle and hold the clip against the detents. It helped a LOT.

Later I resorted to removing the needle, bending the clip in so it exherts more force, and with a micro-brush applying a micro-drop of BLUE Lock-tite on the LS needle threads. You must be careful NOT to get lock-tite anywhere else, and you must clean the threads on the needle and receptacle before you do this...

I do this to everyone who asks for help with their PTS, and the problems seem to mysteriously vanish.

The HS needle is also prone to movement, so bending the clip is also advisable.