I have a 10.5 hp gasoline engine on my wood splitter which sometimes kicks
back when I pull the rope to start it. (Just once every few days, but that
is once too many times.)
This kicks back with a lot of force! And I am pulling with a lot of force as
well! Not good. (I've noticed this same problem with smaller engines too,
but not so much kick back force, so no problem there.)
I got to thinking that I was going to break or injure my hand/arm if I kept
starting this engine. I searched the internet for injuries from starting
these larger engines and there were in fact quite a few injuries including
some broken bones. So I decided to solve this problem by installing an
electric start. No more problem now for me...
But I got to thinking about this and why this happens. And could something
be done to prevent this? (And the reason I am posting this.) A lot of you on
these groups are quite clever, so maybe someone can come up with
I think the problem is that the spark is firing right when the piston
reaches the top of the stroke or slightly before it reaches the top. Then
sometimes this will cause the piston to go backwards instead of forwards.
(And it needs to be this way of course to run properly.)
My idea is to delay the spark just a little for starting. There could be a
switch to start an engine which delays the spark. Then once the engine is
running, you would flip the switch and it would spark and run like normal.
But when starting, kickback would be impossible because it would not spark
until the piston was its the way down.
Anyway I thought I would pass this idea along. Maybe some rocket scientist
out there could come up with something which would attach between the spark
plug and the spark plug wire???
Good plan - Called "variable timing", and used on the Model T, for
exactly the same purpose/reason, if I recall rightly. But I'll be dipped
if I can tell you what the exact mechanism was.
But it's just plain NOT going to happen by putting something between the
plug and the wire - It's something that has to be done at a "lower
Most "lawn-mower type" engines fire by way of a coil (or two coils, in
the case of a two-cylinder rig) bolted solidly to the block (which means
no adjusting of spark advance/retard is possible without major surgery)
with a magnet in the flywheel passing under it. And since the flywheel
is almost invariably keyed onto the crankshaft to maintain timing,
that's also almost impossible to alter without major surgery.
Adjusting spark timing is dead-simple on a car, or other distributor-fed
engine, since all it takes is twisting the distributor a bit. Doing it
on a coil-and-magnet rig like most small engines is nearly impossible
unless the capability was designed in right from the start.
Don Bruder - firstname.lastname@example.org - If your "From:" address isn\'t on my whitelist,
or the subject of the message doesn\'t contain the exact text "PopperAndShadow"
Most, perhaps all modern engines already have electronic start retard built
into the electronic ignition module. (if your engine is old enough to still
have points, all bets are off.)
Start retard can only go so far. Many folks had their arms broken trying to
start Model As even with the manual retard set full retard. Ditto ankles and
old motorcycles with manual retard. I can count myself in the "almost"
category. Which brings me around to my main point.
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 De Armond
See my website for my current email address
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
What do you call a blonde's cranial cavity? Vacuum chamber?
You're having the same problem with other engines... so it's not the
engines, it's you. Get yourself to a small engine repair shop and ask/
beg someone to instruct you in the proper method for pulling that
rope.. Are you left handed?
By your lingo you are N. Canadian, I bet its Pin Shear = improper
timing , a bad or loose Pin on the shaft . Timing as you see and know
of is off, find out why , its mechanical. I bet it locked - knocked, a
few degrees off on a previous stallout to zero rpm, forcing the pin or
something else out of spec. A backfire never should happen, a
Backfire is bad timing = maybe Pin Shear. But im guessing, and never
worked on a motors issue. But I know fact of operation.. I still bet
its the Timing Pin-key on the Fly wheel, but a motor pro will know.
By your lingo you are N. Canadian, I bet its Pin Shear improper
timing , a bad or loose Pin on the shaft . Timing as you see
of is off, find out why , its mechanical. I bet it locked -
few degrees off on a previous stallout to zero rpm, forcing
the pin or
something else out of spec. A backfire never should
Backfire is bad timing = maybe Pin Shear. But im guessing,
worked on a motors issue. But I know fact of operation.. I
its the Timing Pin-key on the Fly wheel, but a motor pro
The flyweights on the mechanical advance could be stuck in
an advanced position.
You need to teach that engine some respect. Some use big and
bigger hammers. One guy used another way: http://tinyurl.com/6ftwow
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This is how I start a motor, maybe I just learned to do this to avoid
kickback I don't know?
Pull the rope full travel or as much as possible. Don't short stroke it.
Let the starter rope retract quickly, Don't stand there holding the rope
handle. On a no start don't start the next pull until the engine has
completely stopped turning.
If I sense a kickback, I just let go of the handle.
Also the starter catch mechanism may need to be lubricated so that it
It's often more than a mere catch mechanism. With many of the pull
start motors sold within the last ten years pulling the rope does not
start the motor directly, pulling the rope winds a spring that once a
particular pre-set tension is reached the spring releases and that's
what rotates the flywheel... so that it rotates at a greater velocity
than one can yank a cord by hand ... it's actually tantamont to
electric start because pulling the cord essentially loads a starter
motor, albeit spring loaded. With these motors the spring is wound
with several short partial pulls of the cord and with progressively
more pressure... with a little practice one will feel how
progressively more pressure is required with each subsequent shorter
pull as the spring tension increases and each subsequent pull should
be shorter and shorter, it won't be too long before one will sense
exactly when the spring will release (guys should be especially good
at this sensing when it's approaching the point of no return, if yoose
get my drift), if full pulls are made mindlessly the spring will
release mid pull (prematurely) so kickback will typically occur, often
painful. Read the manual paying careful attention to the section on
starting... often manuals are not very clear so it's best to have
someone at a small motor repair shop demonstrate. And typically
lefties have trouble with pull start motors, not all, but generally,
because like most all machine tools they are designed for righties.
Old auto engines.
Started by hand crank. Some had no electric starters at all. We had a
1926 Daimler hearse refitted with a 1938 Bedford (i.e. UK GMC).
straight six engine, that had a defective starter AND a weak 1936
battery that had to be started by hand!
Turn over engine slowly by hand through compressions of several or all
cylinders to draw mixture into cylinders.
Retard ignition timing; by the control often mounted on middle of the
Pull compression up to near TDC.
Pull by hand over TDC (watch your thumb position) and engine should
Adjust ignition timing and drive off.
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