Question on JD757 60"

Discussion in 'Lawn Mowing' started by Raymond S., Jun 16, 2006.

  1. Raymond S.

    Raymond S. LawnSite Senior Member
    Messages: 996

    I recently purchased my 757 and have two questions. First off, at what throttle% do you engage your blades? Full or barely on? I've heard it's bad for the machine to do it at full throttle, but at low it almost stalls the engine. Also, when the machine shuts off every time I get a backfire. I know what causes this but is it normal for a new machine or does the carb need some adjusting? Thanks in advance.
  2. MMLawn

    MMLawn LawnSite Gold Member
    Messages: 3,569

    3/4 throttle to engage AND disengage to save your clutch. Then MOW at FULL throttle always.

    That's because you are not properly allowing the engine to cool down before you turn it off. ALWAYS when finished running the mower pull the throttle back to 1/2 and allow it to run for 3-5 mintues before you turn it off. That allows the engine the needed cooling that will not only prevent the backfiring but also give you a much longer engine life. You should NEVER just shut down these commercial mower engines wthout cooling it down after use.

    Also NOT to be a smart butt, but 1) your dealer should have explained these two things esp with you and 2) read your manual as it goes over these things plus has much more good operatng info and info that must be followed in the event of a warranty issue. It is a big investment so do it right and read the manual front to back. Good luck.
  3. Raymond S.

    Raymond S. LawnSite Senior Member
    Messages: 996

    Alright, thanks. My dealer didn't do such a good job w/ me on this, more like a "Ya ever driven on of these, here's the gas, break, on/off. Good luck. This answers my question though. Thanks again
  4. DLCS

    DLCS LawnSite Platinum Member
    Messages: 4,386

    I alwsy shut mine off when the throttle is wide open, thats what my manual says to do. If I shut it off at half or 3/4 throttle it will back fire through the muffler just about every time. All 3 of my 757's are this way.
  5. Charles Odell

    Charles Odell LawnSite Member
    Messages: 62

    DLSC is correct the deere,s you shut down wide open
    Do this and there is no backfire
  6. WPLE

    WPLE LawnSite Member
    Messages: 157

    I have to let mine idol for a minute or two before I can shut down without backfire. 23 horse kawi on 737. That is wierd.
  7. Grassman6

    Grassman6 LawnSite Member
    Messages: 99

    I've got more than 3000 hours on a combination of two 757's and one 777 and my experience has shown that you will buy a PTO clutch every 150-250 hours ($435 at 2005 prices, although they now list for much less) if you engage/disengage at fast engine speeds. Learn one of two techniques 1) engage the clutch as you roll off the end of the trailer ramp and let the momentum & weight of the machine help keep the engine alive, or 2) pull up the choke for a moment and quickly slap it with your wrist at the same time you engage the yellow button. Doing this has increased my clutch life to between 500-650 hours. When you change the clutch be sure to apply some anti-seize to the output shaft or you will be using a gear puller to get the next one off. Have you adjusted the mule belt yet?
  8. WPLE

    WPLE LawnSite Member
    Messages: 157

    Funny your mention the anti-seize.I slung the bearings out of the clutch last season, at about 1200 hours. I didn't think it would be that bad to replace. Boy was I wrong. Pulled on it all afternoon, would not budge. Called dealer said I would be there it the morning. Three hours spent at the dealer. Ended up CUTTING it off with a torch. I was sweating bullets while the torch was heating up that shaft but now damage to the shaft the the lord. Turned out to be a big deal. We greased it up real good with that stuff.

    I run med. lift blades but my 737 can engage the deck at idol speed. Only time it dies is first yard of the day, after that it is idol engage for me. 1200 hours out of the original clutch is proof enough.
  9. hmartin

    hmartin LawnSite Senior Member
    Messages: 590

    I let my JD 757 idle while I blow or trim for a couple of minutes. It will not backfire after letting it idle. I have heard people say shut the engine down at full throttle. Why? What is that supposed to do? Last year, I let the engine cool, then opened the throttle, then turned off then engine with no backfire because I heard people saying to cut it off a full throttle. I haven't done that lately because I don't see the reasoning.

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