Kickback is when you pull start your mower and the pull cord is snapped from your hand. 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..
Also question is, what causes engine kickback?
At an engine cranking speed of 150 RPM, the crankshaft has moved only 1.8 degrees, not a significant change in piston position or gas compression. That small rotation determines that kickback is caused by spark, gas ignition, and burning well before top-dead-center (BTDC) piston position.
Also Know, can a lawn mower engine run backwards? the exhaust cycle on any 4 stroke never completely clears the cylinder of the fuel mixture so all you have to do is pre-ignite on the upstroke and voila, engine running backwards!
Also to know, why does my pull start jerk back?
Usually when an engine kicks back that hard, it is because the valves are out of adjustment. The engine has a compression release that aids in starting the engine. If the valves are out of adjustment the compression release does not work and will jerk you hand back.
How do I stop kickstart kickback?
Kick mechanisms in general have a free spot at the bottom of the kick stroke. Always follow through with the kick stroke to the bottom and wait for the engine to cycle through to prevent a kickback. A kickback on a high-compression large engine can throw you over the handlebars or kill your shins.
Related Question Answers
What does a flywheel key look like?
The flywheel key is a rectangular metal peg that keeps the crankshaft and flywheel aligned when you tighten the flywheel nut. If the mower blade hits an object with enough force to knock the flywheel out of alignment, the flywheel key breaks, protecting expensive parts such as the crankshaft from damage.How do I remove the flywheel on a Briggs and Stratton engine?
Place a flywheel strap wrench around the outside of the flywheel. Remove the flywheel retaining nut from the engine crankshaft with a socket wrench while holding the flywheel with the flywheel strap wrench to prevent the flywheel from turning. Slide the recoil starter cup and washer from the crankshaft by hand.How do I know if my flywheel key is bad?
SYMPTOMS. The symptoms of a sheared flywheel key range widely from a barely noticeable misfire to a no-start condition. In between these extremes the engine may misfire noticeably, run rough, backfire, be difficult to restart hot, or lack power. Advanced timing can cause engine overheating.Which way does a Briggs and Stratton lawn mower rotate?
And COUNTER CLOCKWISE / “CCW”, is the standard of the industry from a Briggs & Stratton lawn mower engine (although the flywheel is actually opposite to the output end) to your VW, Lexus, or BMW, and every gasoline or diesel engine in general use today that may be applicable to vessel propulsion.What causes a flywheel key to shear?
Re: what causes a flywheel key to shear?? The key is shearing because you're asking it to hold the flywheel in place while running. The key should only be for locating the flywheel correctly before bolting it on. The fly wheel should be held on to the crank by pressing it onto the snout of the crank.Can 4 stroke engine run backwards?
Can we start a four stroke engine car with the engine running in the reverse direction? A Diesel engine using your old mechanical fuel injection pump can run backwards. The only problem is that it will be sucking air thru the exhaust pipe and venting exhaust gases thru the air intake. It does not work well but it runs. 
