I have Rotax Max evo I’ve Been struggeling with for a while now.
I picked the engine up from a rebuild at my local sertified Rotax service station.
Since that I can not make it run clean, it stotteres, misfires and stops.
From half Open throttle to Max opening, it only stotteres, almost like 4-stroking, sometimes it can reach higher rpm but mostly it dies.
I have tried swapping all electrics, exhaust valve, carburator, vacuum Lines, Spark plug, fuel Lines and valve sensor.
The shop opened the engine again without finding any faults.
Today i tried another engine in my setup, and it runs perfekt.
Could it be running lean… they have a tendency to exibit that behavior when running lean (or have an air leak somewhere) Its a tough one to guess when the engine came back from the service center.
What exactly did you send to them and what testing did they do? ie was it sent with airbox, carb, boot, reed block etc?
How about the exhaust, is the packing intact?
Tacho reading stable on the gauge?
I wonder if the ground to the chassis via the mount is at play.
Saw that you tried all the ancillaries on another kart, how about the entire engine complete with clamps?