The Mantis two-cycle engine is easy for a novice to work on. Adjusting the carburetor is not difficult, but it does take some concentration and knowledge of the parts. Refer to your owner’s manual, if necessary, to identify parts correctly. You will know when the carburetor is adjusted properly because the engine will run smoothly. One sign that the carburetor needs adjustment is if the engine runs too fast. Another is if the tines turn automatically as soon as you start the tiller, without your having to use the throttle to turn them. Does this Spark an idea?
Adjust the Idle
1. Stabilize the tiller on a workbench or flat surface. Remove the tines, and start the engine.
2. Remove the air-cleaner cover, and locate the idle screw. It is a metal screw, located just below the two colored screws under the air-cleaner cover.
3. Use a screwdriver to turn the idle screw counter-clockwise to slow the engine speed. You will hear the engine slow. Watch the axles, and when they stop turning on low idle, you have a proper adjustment.
Adjust the High/Low Speeds
4. Stabilize the tiller on a workbench or flat surface. Remove the tines, and start the engine.
5. Remove the air-cleaner cover and locate the two adjustment screws next to the choke button. These are plastic-capped screws. One is red and the other is white.
6. Allow the engine to warm up for two or three minutes. Flash the choke several times by closing and opening it while the engine runs. This clears air from the fuel system. When the engine is warm, turn it off with the kill switch.
7. Turn the red screw all the way counter-clockwise until it stops. Turn the white screw so it is halfway between the clockwise and counter-clockwise stops.
8. Turn the switch on and start the engine. Throttle it to full speed for two or three seconds to clear excess fuel, and then allow it to slow to idle.
9. Test the transition from low to high. From idle, throttle the engine to full throttle. Do this several times, listening for a smooth speed transition. If the engine speed hesitates, turn the white screw no more than 1/8 turn counter-clockwise. Full throttle the engine again to test the adjustment. Repeat this until the speed changes smoothly from idle to high when you use the throttle. Use very small screw adjustments.
10. Stop the engine, and replace the air-cleaner cover and tines.