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1991 Lawn-Boy M-series self propelled questions

Discussion in 'Lawn Mowing' started by adkinsca, Apr 30, 2003.

  1. adkinsca

    adkinsca LawnSite Member
    from AL
    Messages: 3

    I own a Lawn-Boy 1991 model M21BMRC (21" self-propelled, BBC, rear bagger). The mower has been great with the exception of the maintenance on the self-propelled system. The issue that I have is not that the system does not work, but that it requires lubrication at the rear height adjusters every use or the unit will not roll backward well. If the unit is used for about 2 hours without re-greasing the height adjuster fittings, the rear wheels will not roll backward, but just slide when pulling the mower back.

    My Brother-in-law owns an very similar mower (1993 Lawn-boy model 10591) with a completely different self-propelled system that has not had any of the issues I have had with my mower.

    Now to my series of questions...
    1. Has anyone had any similar experiences with an M-series? If so, is there a cost-effective way to modify the self-propelled system?
    2. Any good sources of used lawn-boy parts where I might get a drive system from a 1993-1996 model 10590, or 10591?
    3. Any other models of mower which I might be able to swap the drive system onto my mower deck?

    My delimma is that I really like the M-series mower, but am tired of greasing the height adjuster assembly at each use of the mower. The bagger on this mower is the easiest to get on/off of any other I have seen, and other than the drive system, I have not had any problems with this mower.

    Thanks for any suggestions.
  2. lawncare3

    lawncare3 LawnSite Bronze Member
    Messages: 1,981

    I don't want to be rude; but I think it's time for a new mower.

    You could always try pushing it forward with the drive off then pull it backwards.
  3. adkinsca

    adkinsca LawnSite Member
    from AL
    Messages: 3

  4. gusbuster

    gusbuster LawnSite Bronze Member
    Messages: 1,930

    Sounds like either your right pinion is on the left side or vice versa. Check to see if marked L, should be your left wheel R should be your right wheel. Also, this unit had problems with the key and spring on the axle it self.

    What I would do is take each wheel, pinion down to bare axle, clean and degrease everything, replace the spring and key as they may be worn, then re-grease.

    I had M-series for awhile but they were too heavy for winter use. So got rid of them after something serious went such as the transmission or the short block went. I had similar problems like you and just learned to how to set things properly.

    As to cheap parts, good luck. Last time, a wheel was around $45, pinions where around $12. The m series is no longer made so the only supplier is from the Toro\Lawnboy warehouse. In case you didn't know,Toro is now the parent company to LawnBoy.

  5. Jason Rose

    Jason Rose LawnSite Fanatic
    Messages: 5,858

    I have an M series and a toro pro line...same drive system on both. The gear that disengages from the wheel when you let loose of the control bail and let the mower roll forward for a few inches first, will get gunked up with old grease and the spring that pushes the little gear one way or the other gets compressed over time. Take off the back wheels and disassemble the gear and spring mechanism, clean all of it and stretch out the spring a little more. This should, if there are no actuall broken or stripped gears, get it to running right again.

    I love my M series lawn boy too! Don't use a 21" on more than 2 lawns, but I have to have it. I have the toro proline, which sucks i might say, bags horrible, and a commercial john deere, which i like for the BBC but i still use the lawn boy the most.

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