Got this mower for free back in March. When I got it, it wouldn’t start and the front wheels acted like there was some friction going forward and just skidded pulling it backward. I was able to take carb off and clean it out good enough to start. Has a Briggs 550EX engine. I took the cover off the front belt and wheel assembly. Didn‘t really see anything binding so I WD40‘d every place the axle seemed to pass through another part. Wheels freed up pretty good. Fast forward to today. I sold my good mower to a work friend. Had to mow the back yard so i thought I’d pull this out and give it a try. See if it’s ready for a new home. It cut ok, not super. Biggest problem, it ran like garbage. Seems like the idle is slow or something is sluggish. It’s possible the gas that it came with was no good so it might just need ran all the way out. Pulled plug and it actually looks fair. Even tried mowing for just a little bit with no air filter, thought maybe it was too clogged. Didn‘t really change much. I do not have an RPM tester. Any ideas what else to look into? Would idle fine then sputter a touch then back to good idle, but also just sounded weak overall. I'm not too familiar with these engines. Maybe they are just a low RPM engine. Just looking for something I can do, something I should check that I may have overlooked?