Hello, I have a cfmoto zforce 550 2019 and as you can see in the video on the link I shared I have this problem with that sound and the engine running rough. It won't start unless I pump gas (pumping the gas pedal), and once it starts it is running rough and does this knocking sound. I have changed the fuel filter, checked fuel pump, adjusted the valves, changed the ecu and so on. What is wrong??? It died suddenly while driving on the road and wouldn't start.
https://drive.google.com/file/d/12TZiRtEAlcmJyoOtthMexGj0P1TGSFX2/view?usp=drivesdk

[2015 Z Force 800 53/Trail EPS]

Sounds like she either has the old 500 cam chain problems that so many have had or...and I hate to say it...she has a problem with the bottom end. I wouldn't race the engine anymore...or better..run it at all anymore until the problem is found and fixed.