Engine Kicks Back When Starting
Engine Kicks Back When Starting
When you experience kickback you won't mistake it for anything else. Kickback is when you pull start your mower and the pull cord is snapped from your hand. It can sometimes whip you as it does so, which is Oouch!!.
Why does the mower engine kickback when starting? The reason the engine kicks back is because the blade has hit something solid which caused the engine to come to a sudden stop and break the flywheel key.
- Engine won't start
- Pull cord snapping back
- Engine backfiring
- Oil leaks
- Broken pull cord / handle
- loose / damaged blade
The recoiling of the pull cord stings a lot.
What Is A Four Stroke Engine?
How does four stroke Work?
Valves open and close as engine moves through the cycle.
What Is Engine Timing?
When the timing is off, it means the plug is firing outside its narrow window of operation.
What Is A Shear key?
How To Replace The Shear Key
Remove the plug wire to disable the mower and turn off fuel.
Remove plastic engine cover, couple of screws usually.
Remove pull cord assembly. Two bolts at rear and one at front.
No need to remove the dip stick on this model, it comes off with the assembly.
Mark the nut in relation to the crankshaft, this lets you know how much to tighten, in reassembly.
Use a block of wood to wedge against blade to prevent engine from turning as you loosen flywheel nut.
Loosen the flywheel nut, and remove, using a socket set.
At this point you will be able to confirm that the shear key is your problem, the key ways don't align.
However, I have worked on mowers with kickback and found the shear key to be good. This unfortunately means that the crankshaft has twisted, this is rare.
Replacing a crankshaft may not be economically viable for some mowers.
Spray the key way with WD40 and let it soak a while.
Remove the coil by removing two bolts. Set the coil to one side no need to remove the wire connector.
When reassembling, an air gap must be maintained. Check out "Fitting a Coil"
Ideally, use a specialised tool called a pullers. I am going to assume you don't have, so try this, but use caution as you can damage the engine.
Ask a helper to apply the bail lever or use zip tie or tape. Put the flywheel nut back on by hand and back it off 1 turn.
Using two hammers and some safety goggles, place one hammer on the flywheel nut and strike it sharply with the other, once is enough, don't over do it.
Now go ahead and remove the nut.
Striking it with the hammer helps loosen its grip.
Sometimes it will be necessary to use a long screwdriver to lever down on the engine. Lever from one side to the other to remove flywheel.
The word here is finesse, please be gentle.
Remove the flywheel and remove the old shear key from the key way. Check also the key way on the engine.
If you can't get the flywheel to move, don't worry it happens.
Go ahead and buy, rent or borrow a flywheel pullers, it makes this job look easy.
New and old shear key.
Fit new shear key by simply pushing the new key into the key way on the crankshaft.
Align flywheel key way and push on.
Tighten nut to your mark.
Reassemble in reverse order and check out "Fitting a coil".
Check your blade and blade boss for damage.
Make sure its secure. A symptom of a bent blade is excessive vibration.
That's it, Nice Work!