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Question about my self-propel mower

Hey all, I have a simple (for anyone but me) question:


I just purchased a Lawn Boy 20in. Self-Propel Mower back in March.  First two times using, ran great, no problems.  I've used it 3-4 times since, though, and it no longer self-propels (but it does still mow the grass well).  It's always been fully fueled, and the appropriate oil is in the tank, filled to the correct level. All of the lines and chains are tight. I've cleaned under the lawnmower chasis; there's no lingering or extra grass or debris...


Anyone have ideas on what could be wrong?


Thanks for help in advance!


-Jay (rookie homeowner)





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Posted 2012-06-04T15:53:58+0000  by Jay_J Jay_J

Hello Jay_J. Ken here in the Chicago area. Welcome to the Community.

I’m sorry to hear about your mower problems. The only two things I think

could be the problem are either the drive belt has come off or it’s broken or

the drive cable is not tight enough. Check to see if either of those are the problem.

If those two things aren’t the problem, then go to and contact

Lawn Boy. Good luck and take care.

Posted 2012-06-04T16:25:21+0000  by Ken_HD_CHI

Hi Jay,


Travis here, from The Home Depot in Atlanta.


Your Lawn Boy self propel system is belt driven. The belt can slip off of either pully and cause it not to drive. One pully is on top of the transmission case and is difficult to see. The other pully is easier to locate, directly under the engine and above the blade bolt.


If the belt is off of either pully, and the belt is not damaged, it can be re fitted onto the pully. First, unplug the sparkplug wire.

Turn the mower on its side so that the air filter is facing upward. Inspect the belt from this position. The belt will be very loose if it has come off of the pully. Fit it onto the transmission pully first, then onto the crankshaft pully. If the belt appears to be intact and properly fitted onto the pully, the self propel cable may need adjustment.


Here is Toro/Lawn Boy's help site to show you how to adjust the drive cable. All you will need is a wrench.


Let us know how it turns out.




Posted 2012-06-05T17:34:07+0000  by Travis_HD_ATL
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