Motor run but blades don't

Does the engine run? If it runs the gear is most likely stripped out. Or it is the shear pins on the shaft. Gear can be replaced most are plastic an replaceable. Some are hard to find. Not hard to do just takes a little time.

After seating the screws back them out 1 1/2 turns. This should be close enough to get it started. Let the motor warm up a little then, with it idling, turn the low screw in until it starts having a hard time running then back it out until it idles smoothly. Prop up the Mantis so it can run at full speed safely while you adjust the high side. With the throttle wide open, again turn the high screw in until it starts running roughly and back it out until the motor is running smooth. Some say to turn the screws out until the motor starts having a hard time running and then turn it back in half way to where it was running bad at the other end. This doesn't work as some engines don't care how far open the screws are.

You don't say where the smoke came from but check out the worm gear box and see if gear is eaten up. Supposed to be greased regularly but gear can wear out over time or overloaded digging. . Don't know your model but here is manual on one of them. See if it helps. Look fer it!
http://mantis.com/global/assets/owners_manuals/08_tillers/401702.pdf

Hello,
My name is Dane and I am going to assist you in solving your problem.
You should have an idle screw adjustment on the carb to adjust the idle RPM. As you pull the trigger, watch on the carburetor for a small moving plate. The idle screw should touch that plate. Be very careful, and have someone hold the tiller and start it. Back off the screw just enough until the tines stop turning. I hope I've helped. If you found this reply useful, please leave me some THUMBS UP, if you feel I've deserved them. Thank you! Dane

Sorry Bob, it needs shop time. The part under the motor and between the two blade sets is the transmission. The input shaft from the motor is geared to turn the blade shaft; either may be frozen if there wasn't enough grease in the trans or it's possible a gear tooth broke and jammed the system. You have to remove the trans, take off the blades and get inside it to see if the grease is contaminated or if it even has any in it. Check for peices that may have jammed in the gears also. If all of the parts are intact, clean out all of the old grease and pack as much new grease in as you can get in it.

check the carburator, it sounds like a main jet is clogged or the carburator is dirty. Is the air filter clogged? Is the motor under strain?

Sounds like it's flooding either from over choking or the inlet needle in the carb is leaking. Have you removed the plug and blown out the cylinder and plug with air and then tried to restart? Be careful not to keep cranking with the choke pulled out. When it 'hits' ONE time, move the choke halfway in and crank again

Hi Don. There are two adjustment screws on the carburetor. Start the engine and while it is idling, turn the screw closest the engine (low speed adjustment) counterclockwise until it starts to falter, then back a 'hair' and try the throttle again. If that doesn't work, I would recommend doing what I usually do... put a new carb on and be done with it! Carb is a Zama C1U-K54A

take pull rope cover off and oil the clutch that screws on the crank shaft