4-stroke Mantis tiller

4-Stroke Mantis Tiller Problems: 10 common issues and direct solutions

The Mantis 4-stroke tiller is a very popular machine, it is lightweight, robustly made, and has a powerful 4-stroke Honda engine, which is famed for its reliability and performance. It has made preparing the soil for planting a much easier and more enjoyable experience. As with any mechanical machine though, it has had its fair share of issues. This article looks at the most common 4-stroke Mantis tiller problems.

4-stroke Mantis tiller problems

Remember that tillers can be dangerous and it’s important to wear the correct safety gear before starting to use one. The list of problems associated with the Mantis 4-stroke tiler is as follows;

  1. The engine is hard to start
  2. Engine runs poorly
  3. The engine has no power
  4. Tiller blades are bent or loose
  5. The tiller handle vibrates
  6. The Tiller engine won’t rev
  7. Tiller dies when it engages with the soil
  8. The tiller engine wont stop
  9. The engine smokes
  10. Starting rope pulls out but the engine won’t start

The engine is hard to start

If you find the engine on your Mantis tiller hard to start you should check the following:

There is fuel in the tank and the fuel is not old and stale – replace it with new fuel if necessary. Check the fuel is turned on.

The spark plug is in good condition and working. remove the plug and check it is clean -not black and sooty. Check the end of the plug has a gap and that it is giving a spark. To do this check you should insert the end of the plug into the plug lead and hold the threaded side of the plug next to the metal of the engine.

Now pull the starting cord – you should see a spark coming from the end of the spark plug. be careful not to touch the end of the spark plug as it will give you a shock.

Check the air filter is clean – screw the cover off the air filter housing and look at the filter- if it is dirty you should replace it with a new one.

Check the fuel filter in the fuel tank is not blocked. The fuel tank has a small filter inside it – check it is clean and not blocked – replace it if it is dirty and blocked.

Check the exhaust port is not blocked – sometime bees will make their nest in there, which will prevent your tiller engine from starting.

Finally check the carburetor is getting the fuel and that there is nothing sticking inside the carburetor -sometimes after a long sit not being used the small float in the base of the carburetor sticks, or the choke sticks on or off.

Engine runs poorly

If your tiller is starting but the engine is running poorly it is most likely that the spark plug needs to be replaced or the fuel is stale. Some guides refer to adjusting the carburetor but if your engine had been running well previously I wouldn’t jump to start adjusting the carburetor.

The other thing to check is the air filter and fuel filter are clean. Replace them if they are dirty.

The engine has no power

Sometimes your engine starts and runs well before you start into work but then when it’s put to work in the soil it has no power.

This can mean the tiller has a bad spark plug, stale fuel, dirty air, or fuel filter or it may have a damaged/ badly adjusted throttle cable which would mean the engine is not revving out to its maximum.

Perhaps there is something causing the tiller from physically operating at its max rpm – check there is nothing stuck in the tines/blades. If there is nothing visibly holding back the blades, maybe the worm gear in the base of the tiller is damaged or needs to be greased. Remove the cover and take a look inside.

Tiller blades are bent or loose

Due to the abrasive nature of tilling, it is only natural that you will get a bent blade or you will find one or several of the twin blade sections becoming loose.

To fix a bent blade, you should remove the R clip which holds the twin blade unit on that side. Then pull the unit off the shaft. Now position the bent section of the blade onto something solid and hard like a concrete block or a steel machinists vice and straighten the other side of the blade using a heavy hammer.

the points of the Mantis tiller blades can become bent
The points of the Mantis tiller blades can become bent.

To refit a blade section that has come loose, you will need to push the twin blade section back over the shaft until it reveals the hole in the shaft so you can insert the R clip.

It is important to note that you should fit the R-clip with the round of the R clip facing clockwise, this means as the tiller blades turn around ( they turn clockwise) the legs of the R clip are not pulled apart by roots or soil which would make the R clip come out again. This cannot happen if the R clip is inserted into the shaft correctly.

The mantis twin blades are one-piece units that have two blades riveted together. The riveting means there are no nuts or bolts to work loose, although it also means it is not a simple job to separate the two blades from each other.

The tiller handle vibrates

This is a simple one to fix. The tiller handle pivots in the middle by slackening two large round hand screws. When these are slackened off you can fold the tiller handle down flat- which is great for transporting in your car etc.

Sometimes these hand screws can make their way loose- resulting in the handle jangling and rattling when the tiller engine is started. Always check both crews are tight before starting your tiller engine.

The tiller engine won’t rev

There is only one reason why your tiller would start, run, and not rev, and that is because the throttle cable has come off or has broken. Inspect around the throttle lever and at the carburetor side to check if the cable is broken or if it is able to move the throttle on the carburetor

Tiller dies when it engages with the soil

This problem occurs when the driveshaft works its way out of the clutch assembly fitted to the engine. Check that the shaft is fully seated into the clutch, then check that the worm gear drive at the end of the driveshaft next to the tiller blades is correctly aligned with the gear wheel.

If everything here is correctly replaced it may be that the clutch is slipping. You will know if the clutch is slipping because the engine will rev correctly and the blades will turn when they are out of the soil, but when you put the tiller into the soil the engine revs don’t dip but the tiller blades stop turning.

The tiller engine wont stop

The mantis 4-stroke tiller has an electronic on/off switch located on the top of the handle. Sometimes this switch can become faulty and it won’t turn the engine off.

If this does happen to you don’t panic – to turn off the engine without using the off switch simply let the engine return to idle speed and reach down and turn the choke to “ON” this will stop the engine more or less immediately. Order the replacement switch at your convenience.

The engine smokes

If you notice your engine producing smoke from the exhaust it is because there is oil getting into the combustion cylinder of the engine. As the Mantis 4- stroke engine does not need 2-stroke oil to be mixed into the fuel, the only place this oil can come from is the engine sump – used to lubricate the engine.

Under normal conditions this oil cannot enter the engine combustion chamber – but it can enter if the engine sump has been overfilled with oil – check your dipstick to see if this is correct.

The other instance of oil entering the combustion chamber is if the oil rings on the piston are damaged or some other mechanical damage has occurred. If this is the case it will require further investigation.

Starting rope pulls out but the engine wont start

When you pull the pull cord of your tiller, you are essentially jumpstarting or manually rotating the piston inside your engine. The pull cord sits inside a spring-loaded grooved disc which is connected to the engine flywheel via retractable lugs.

This means when you pull the cord out, these lugs shoot out and connect with the flywheel turning it around, and at the same time, it tensions a coil spring connected to the pull cord disc.

When the pull cord is fully pulled the retractable lugs disconnect from the engine flywheel allowing the engine to continue spinning without turning the pull cord also. Then the tensioned coil spring forcibly retracts the pull cord back into the disc, ready for your next pull.

  • If the cord pulls out and the engine doesn’t turn it is because the lugs are not engaging.
  • If you pull the cord out and it doesn’t go back in it’s because the coil spring is either broken or out of place.
  • If you pull the cord and it comes out of the pull cord housing the rope is broken and you’ll need to replace it or retire it inside the housing.

To fix any of these issues you will need to remove the pull cord housing from the engine and investigate.

So to recap, the top 10 4-stroke Mantis tiller problems are: The engine is hard to start, the engine runs poorly, the engine has no power, the tiller blades are bent or loose, the tiller handle vibrates, the tiller engine wont rev, the tiller dies when it engages with the soil, the tiller wont stop, the engine smokes and finally the starting rope pulls out but the engine wont start. I wrote a helpful review of the Mantis 7940 tiller if you’d like to check it out.

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