I have had a problem with my tractor it does not loose RPM"S but just doesn"t want to go this is usually on a hill it does ok on the down hill side I changed the fuel filter and cleaned the glass bowl and filter. this helped some then it started once more let it set for about an hour at this time I added fuel and some disel additive and it worked alot better did some stall but not alot like before. Any other suggestions I am really at a loss on what to do next.