Bad Boy Maverick running rough w/ blades engaged

[matman13]

2019 Bad Boy Maverick, Kawasaki FS730V, 48 hours of operation.

I was mowing today. Engine started sputtering due to low gas. Disengaged blades and drove back to the garage. Added 5 gallons of 100% unleaded gas purchased about 3 weeks ago. Started the engine and noticed it didn't sound right. Had a couple of missed fires, but didn't think much of it. Engaged the blades, and after a big power drop, they started running. When I pushed the mower forward, big power dropoff and very low speed. Turned off the blades and headed back to the garage. Opened the air cleaner. Filter looked pretty clean, but the pre-cleaner foam pad was dirty. Cleaned that, and re-installed. Fired it up. Engine still sounded a little funny, but power was much better. I noticed that it was blowing black smoke occasionally. Ran it for a bit without much issue (still didn't sound fully right), but my wife flagged me down and said it sounded funny to her. Pulled it in the garage for the evening.

Any suggestions for what to look at in the morning?

 

[Scrubcadet10]

Black smoke means it's running rich, which means you have a higher gas content in the air/gas mixture provided by the carb.
I would check that the choke butterfly is fully opened/opening in the carburetor.

 

[StarTech]

I second that as it has a plastic choke shaft and I have seen both it and sometimes a missing return spring. Also do cylinder balance test as it might just be running on one cylinder.

 

[Rivets]

Willing to bet the engine has either a blown head gasket and/or is only running on one cylinder.

 

[Mower King]

If you bought it new in 2019 and are the original owner, it should still be under warranty. The Bad Boys we sell (we are a new mower dealership and not a box store) have a 2 year warranty. Warranty covers manufactures defects, if that is what it is......if it is a defect caused by the owner, it's on your dime.