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Hi Guys,

I picked up this S21ZSN last week with a few spare parts ( carb, recoil, fuel tank, new rear drive wheels) for 50.00
It is in pretty good physical shape and runs but the will not pull itself. I am not new to lawnboys but new to there self propelled models. When I start it with rear wheels raised they spin but when put on the ground it do nothing. The cable is connected at both ends and the drive belt is turning the trans pulley. I notice that the trans will rotate slightly front to back it seems to me that it should be solid. I will look up a parts diagram to see what I am missing. I find that the mechanism arm on the transmission does not move but a 1/2 inch or so. Is that normal ? If I can't get the drive working I have a extra 10415 21" I will put the engine on but was hoping to have this self propelled to compliment my 19" push lawn boy. So did I do ok for 50.00 ?
Any tips appreciated.

22R said:

Hi Guys,

I picked up this S21ZSN last week with a few spare parts ( carb, recoil, fuel tank, new rear drive wheels) for 50.00
It is in pretty good physical shape and runs but the will not pull itself. I am not new to lawnboys but new to there self propelled models. When I start it with rear wheels raised they spin but when put on the ground it do nothing. The cable is connected at both ends and the drive belt is turning the trans pulley. I notice that the trans will rotate slightly front to back it seems to me that it should be solid. I will look up a parts diagram to see what I am missing. I find that the mechanism arm on the transmission does not move but a 1/2 inch or so. Is that normal ? If I can't get the drive working I have a extra 10415 21" I will put the engine on but was hoping to have this self propelled to compliment my 19" push lawn boy. So did I do ok for 50.00 ?
Any tips appreciated.

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When the drive is engaged, does the belt seem tight? In other words is the belt still so lose that it slips instead of pulling the mower.

Thank you for the reply. I will check that out and get back with you.

22R

OK so the belt seems tight as when I start the engine the trans pulley turns. The odd thing is to me is that the drive engagement doesn't seem to do anything. the cable moves the arm on the trans but the wheels turn if lifted on blocks but when I drop it down it doesn't go anywhere like maybe something is stripped ?? the teeth on the wheels look OK but I will compare them to the new set I have next. The slop that allows the whole tranny to rock back and forth doesn't seem right but I don't think that is the whole issue. Wish I had another one like it to compare it to. The guy gave me another trans axle but it is in pieces so I wonder if this one was swapped out or taken apart but it doesn't look like it has been worked on just by looking at it.

Re: S21ZSN Drive Help w/Pics (update)

OK so if I pull the wheels and start it while the rear is lifted the gears for both side spin but if I grab the gear they stop while the shaft spins. I removed one side and there is a woodruff key and spring in the key slot. If I put the wheel on and turn the wheel by hand engine off there is slight resistance but if I engage the lever the trans locks up so I am thinking that the trans may be ok and it is something with the gear or ratchet part that would allow it to back up. any more insight would help.And one other thingis the inside of the keyed drive gear supposed to have a step on one side then a taper on the other ?? Like so it will catch one way and free wheel if pulled backwards I guess ? Are the gears specific to each side ? maybe they was installed backwards ?

22R

Got it figured out ! Thanks

22R

22R said:

Got it figured out ! Thanks

22R

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Come on...you've got to tell us what you did/figured out.

Someone else may have that problem.
Plus...we want to gain knowledge!

I think the gears are the same but they can be put on backwards. was that it?

bwright1818 said:

I think the gears are the same but they can be put on backwards. was that it?

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BINGO !! The drive gears on the end of the shaft. Very easy fix once I figured it out.