Neon John wrote:

[....]

The problem isn't with the engine. It's with the starting technique. Any
engine will kick back if the crankshaft is turning slowly enough when the
spark fires that it can't make it over TDC before burning gets underway. This
happens when you grab the cord and yank or stomp the kick starter from some
random engine condition without setting things up first. That's why one never
lets that happen.

The technique, developed around the turn of the previous century, is to slowly
rotate the engine until the piston is at top dead center on the power stroke.
That's where the crank suddenly rotates freely a little bit after the
resistance of compression.

After the engine is positioned that way, the cord is retracted (or the kick
starter returned to rest) and the strongest pull you can muster is given. The
engine has almost two complete rotations to store energy in the flywheel
before the compression stroke is encountered.

The result is an easier pull, no chance of kickback and usually, starting on
the first pull. One must be sure to immediately return the starter cord to
the rest position (don't let it fly - the recoil spring and/or rope will
eventually break from that abuse). If you hold onto the cord and the engine
doesn't quite start but fires in reverse, it'll yank the cord out of your hand
rather violently. Blisters and ripped skin can result.

I used to ride and race big single cylinder bikes before electric starters
become available. The "find TDC before cranking" became so second nature that
I now automatically do it even with tiny engines like the one on my weed
whacker. Not chance of kickback there, at least none that matters, but
pulling the cord is sooooo much less effort that way.

John

good write-up John. facts are always useful.