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eXmark FrontRunner Ultracut Deck Vibration

Discussion in 'Lawn Mowing' started by Hushko, Jun 24, 2006.

  1. Hushko

    Hushko LawnSite Member
    Messages: 43

    I was out mowing with my new eXmark FrontRunner this afternoon, which just turned over 10 hours on the meter. It uses the 60" shaft-drive Ultracut deck and is driven by a 25 HP Kohler. I was really impressed with the demo mower and the absence of vibration when the blades were engaged as opposed to my 60" Lazer Z with the same deck and engine. When my own FrontRunner was delivered, the blades fired up just as smooth and ran from idle to full throttle without a trace of vibration. Just fantastic. But then today while finishing up the yard (I mow about 4 acres), the deck began to resonate up and down with this irritating vibration for no reason whatsoever. The vibration transmitted through the floorplate and control levers. I immediately stopped the mower and inspected the underneath of the deck for possible problems. No loose shafts or broken blades. I also checked the top of the deck for any debris or obvious problems and watched the pulleys while the deck was engaged. The belt was vibrating and flapping something fierce and the tension pully and spring was bouncing back and forth in tune with the vibration. It almost acted as though a chunk was missing from the belt, although it was fully intact. My yard is flat and clear and I hit nothing with the blades to cause anything to bend or break. This mower's way too new and awfully expensive ($11,000) to be acting like this already. It's the weekend and my dealer is closed till Monday, so I thought I'd put this out there and see if anyone else might have had or is having a similar problem. I hate to continue using it in fear of causing the problem to worsen. It's bad enough that this deck is laden with weld splatter making it super difficult to scrape. And even worse that the lift-deck design allows the linkage to literally wedge and burry itself into the top of the deck leaving a nasty gouge in the steel. Now I feel like I just finished running a jack hammer for two hours. Any help would be greatly appreciated. Thanks!
  2. Mowingman

    Mowingman LawnSite Platinum Member
    from Texas
    Messages: 4,720

    Check the groove on each pulley on the deck. You may have picked up a small rock, or a small piece of wood and it has wedged itself into a pulley groove. This will make the belt jump, and deck vibrate every time the stuck piece comes in contact with the belt. This has hasppened to me on several occasions.
    Other more serious problems could be: Pulley coming loose from a shaft; bearing going bad; blade has gotten bent.
    Hope it is something simple, but at least it is under warranty.
  3. PLM-1

    PLM-1 LawnSite Bronze Member
    Messages: 1,640

    Is the belt adjusted properly? That is about the amount of hours that you need to adjust new belts for the first time ... just a thought
  4. newz7151

    newz7151 LawnSite Silver Member
    from Tejas
    Messages: 2,419

    dunno where this came from, might or might not be your problem.

    "Drive Shafts Bending
    We discussed in a previous advisory the need to properly install the drive shaft on the gear box at the deck to prevent the drive shaft from being bent when the deck is tilted up for blade maintenance. We continue to receive reports of drive shafts bending and now have available a kit that provides a washer with a single internal tooth that slides on to the keyway prior to the key and shaft installation that creates a positive stop when installing the shaft.
    This change occurred on production FR524”s at S/N 640,687 and FR604’s at S/N 647,854.
    The part number of the kit containing the washer and installation instructions is 109-4494. Exmark warranty will reimburse its dealers the cost of this kit when installed on new unsold decks in your inventory or when used to prevent a second failure of a unit that has bent a drive shaft. Warranty labor will not be allowed as the installation time for the washer should be less than one minute. File a stock mower claim if updating unsold inventory and include the kit on warranty claims that document a bent drive shaft on a field unit.
    A secondary benefit of this washer is that it provides protection to the input shaft seal of the gearbox. Exmark has received two reported cases of customers mowing extremely tall grass and that the grass has been able to wrap around the front PTO knuckle to the point where it rubs the seal causing an oil leak."
  5. Hushko

    Hushko LawnSite Member
    Messages: 43

    I really appreciate all the info you guys provided. I took Mowingman's advice and checked first to see if all the pulley grooves were free of debris, and they were all clear. I then removed the deck belt and spun all of the pulleys by hand to check for unusual play in the shafts and they all checked out fine as well. The blades all checked out to be straight too. There is no belt adjustments on this deck according to the manual, since there's a spring loaded tensioner pulley to maintain a constant force on the belt - thanks PLM-1. Finally, I had my wife sit in the seat and engage the blades while I took a closer look at the belt and pulleys. At idle, you could tell there's a definite problem associated with the gearbox because of the nasty grinding noise and vibrations being emitted. You could even visualize the belt flapping in unison with the up and down vibrations that are resonating from the gear box. To confirm it, I removed the belt and engaged the pto at idle to just run the gearbox itself and the noise was consistent with the noise with the belt on. I checked my email and there was a new post from newz7151 regarding an advisory on bent drive shafts. This sounds like it may be the case with my mower, although the deck seemed to run perfectly fine during the first hour of mowing and then began to vibrate after that. It seems that if the shaft was bent it would have vibrated from the start of mowing that day, especially since I never raised the deck up from the time I started mowing that day. Nonetheless, my mower's does fall into this category of earlier serial numbers that were produced before the modifications were made to the drive shaft assembly. The more I think about it, it seemed that the vibration began immediately after I mowed an area that was an additional week overgrown, with the grass measuring in the neighborhood of 8 inches or so. Even though I raised the deck in the high grass, the mower was under more stress than usual, but nothing that should destroy a gearbox on a commercial mower that's less than 10 hours old. I'll be calling my dealer on monday to see what they'll do about it and will hopefully be back with a verdict. Also, newz7151, if you have any idea where you found this resource, I'd really apreciate it. Maybe I could pass the info on to my dealer for reference. Thanks again!
  6. newz7151

    newz7151 LawnSite Silver Member
    from Tejas
    Messages: 2,419

    Oh, I know where I got it from, I'm just not at liberty to say. Have your dealer check for a product advisory released sometime around June 5th.
  7. Hushko

    Hushko LawnSite Member
    Messages: 43

    I understand. Thanks again!

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