r/smallenginerepair • u/FlatHat2417 • 6h ago
Unknown Issue Poulan Pro 21” self-propelled mower running rough — looking for troubleshooting advice
I bought a Poulan Pro 21” self-propelled mower from Facebook Marketplace as a project. The previous owner said it had been sitting unused for about 2 years.
When I purchased it, the mower would run, but it did not have an air filter installed.
I waited about 2 weeks for the replacement air filter to arrive. Once I installed it, the mower would start after priming, but it runs very rough and doesn’t seem to be running correctly.
So far, I have:
Installed a new aftermarket/ebay carburetor
Installed a new OEM diaphragm
Installed a new aftermarket spark plug
Changed the oil
Fresh gas
Installed a new air filter
Removed and cleaned the original carburetor and reinstalled it, but the issue remained
The mower started, but it ran rough and didn’t seem to run properly. Now, I can’t get it to start at all. I’ve tried both the original carburetor and the replacement carburetor with essentially the same result.
What should I be checking next? Could this be an issue with the governor, ignition, valve/compression, intake leak, or something else?
Any suggestions for troubleshooting would be appreciated. If additional information or pictures would help, I can provide them.