Slow hydro drive

Discussion in 'Lawn Mowing' started by kmglacey, Dec 14, 2003.

  1. kmglacey

    kmglacey LawnSite Member
    Posts: 4

    I recently purchased a used Bunton walk behind to use to bag in the winter. It ran fine for a few weeks, but now runs very slow, and doesn't seem to want to go up hills. My first thought was a loose belt, but when I replaced it, same thing. I have checked the fluid for contamination, and it looked clean. The oil in it is(as per the manual) 20W50. Could that be too thick for colder weather? If I do switch to a synthetis Mobile 1, do I have to purge the system, or just empty the tank and fill it with the new oil?
    Any advice would be much appreciated.
  2. J.Gordon

    J.Gordon LawnSite Senior Member
    Posts: 675

    I would switch to the synthetic oil if it were my machine. Yes I would definitely drain all the old oil out and change the hydraulic filter. (The hydraulic filter is probably causing the restriction in the flow.)
    Make sure you pre-fill the hydraulic filter with oil before putting it back on. (So your pumps don’t run dry!)
    Did you run the mower long enough to heat up the oil? When it’s cold out it does take longer to get the oil flowing. The 20/50 is pretty thick when cold but should warm up after a while, enabling the pumps to work.
    I have never seen a Bunton up close but I would check the valves to see if they have full movement. They may not be opening all the way.
    Maybe someone else can give you better advise. Good luck! :)

  3. Black Water

    Black Water LawnSite Senior Member
    Posts: 250

    Like J. Gordon said, are you letting the system warm up?

    You said you've checked the oil level, and i assume there's a clean filter installed. Some thing's i would check if it were mine would be...

    1) Check the linkage from the controls to the pump like j.gordon said. Are ya getting enough travel in on the for./rev. valve?

    2) Check the the key in the pump pulley.

    3) Check for a bad wheel bearing.

    4) Check the spring in the relief valve. Spring could be broken, or poppet/ball could be stuck open. This would allow pressure to by-pass the wheel motors( do ya have wheel motors ) and machine would run slow because just a small amount of pressure is going to the motors.

    5) If at all possible, check the pressure, and compare it to co. specks.

    6) And last, start tearing down pump's and wheel motors and check for ware in the gears , or any trash plugging any orifices. Maybe the last guy had a leak and tried to seal some thread's on a leaky fitting with teflon pipe tape instead of pipe dope, and a piece of the tape broke off and is lodged itself in a orifice/valve somewhere. This is a long shot, but iv'e seen it happen.

    Hope this help's.

  4. sbvfd592

    sbvfd592 LawnSite Senior Member
    Posts: 668

    Check for a bad wheel bearing. thats a prob i had with my john deere
  5. edrenckh

    edrenckh LawnSite Member
    Posts: 135

    Toro's have a bypass valve that controls how fast the machine goes. It's just behind the pumps. All the way in, no by-pass and jumpy machine.

    All the way out, total bypass, and no-go. No hydraulic lines, just a lock-nut and adjustment bolt on each pump.

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