In the Chinese Tractors forum there's a thread about changing the injector pump oil on a Farmpro 2420.
Does this injector pump oil change apply to any model Kubota tractors ?
( Mine is a L4200)
Although I have no experience with Farmpro I do know that the injector pumps on Kubota tractors and Cummins diesel motors are lubed by the diesel fuel that runs through them.