What a great forum I have been reading for 6 months or so lots of good info. I have a 642B that I rebuilt from the ground up original a gas motor installed an izuzu diesel in. approx 3000 hrs. on the machine. I will post some photos later. I noticed that the right drive side seems to be weak or not working properly. When I push the levers forward right side has power initially then seems to kick out like a pressure relief or something. It still has some power after that because it will move forward in a fairly straight line. It seem to operate better in reverse as well. any ideas ?