cub cadet ztr50 with kawasaki fr651v engine surging at idle and mid range ?

[rancher352]

6 year old mower with no prior problems until it started surging at idle and mid range. I change plugs every year, use non ethanol fuel, change oil every 50 hours. I recently replaced the fuel filter which was non standard. Any suggestion on what I might look at?

 

[mechanic mark]

If engine started surging after replacing fuel filter replace with OEM Kawasaki filter. If Kawasaki, keep it all Kawasaki. Also check air filter for replacement.