having trouble with my is4000.unit bogs down when under load going up hill, thick grass. Seems to be a problem with governor . I have no idea how to adjust, repair or replace it. I think it is internal. Could someone out there pleeeese tell me how it works and how to access it.previously it adjusted for load asin adjusting gas going up hill to maintain steady speed. Any help is appreciated and thanks in advance. Forgot to mention it has a dihatsu 3cyl. Gas engine.