Small Engine Troubleshooting Problems? Ask a Mechanic Now.
These mowers are notorious for this issue. Transmission is most likely gone bad. You can check chain to make sure it is installed still, but I would guess bad transmission. I have 4 of these in the scrap pile at shop for same issue
You can replace the drive disc and it may work, but be prepared for the worst. The drive disc is not too much to take the chance, much cheaper than a new mower for sure.
I hope you got issue resolved.
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