I'd appreciate any help or direction here... I managed to bend the
crank shaft on my Craftsman lawn mover (model 917.378641) and this
type of repair is not covered under warranty... so I was wondering if
this is something I can repair myself. How difficult is replacing the
crankshaft? I've done lots of suspension, exhaust and engine work on
my car and have all the standard tools... any special tools needed? Is
there anywhere I can find a service manual that can step me through
this kind of repair?
Thanks and appreciate any help,
Such repairs are not difficult if you have the skills needed to rebuild
an automobile engine. It may be better to deal directly with the engine
manufacturer or his local sales rep.for parts rather than Sears. I think you
can get small engine manuals at many auto stores. Check the price on a new
engine and decide if you want to tackle the job. If the lawn mower is old a
new engine may be the better choice but you indicate that the mower is still
You know, this sucks and is part of what is wrong with America. This guy
runs his mower into a tree stump or a brick or something and now you're
encouraging him to fuck Sears because of his mistake. He needs to eat this
one. The more people that play this game, the more we ALL pay for stuff
from Sears. Grow up and take responsibility for God's sake.
One: his diagnosis may be wrong!
Two: Sears will check the engine out, or at least that is their job to do.
Three: Sears will then decide whether to send him an estimate of the repair,
or they will decide to replace his mower under warranty. That is their
choice and their decision.
Four: Not telling Sears of his suspected diagnosis is not cheating nor is it
morally wrong. However, his diagnosis may taint the service staff's opinion
with the idea that the shaft is bent, and they may not check to see if it is
something else, which they should do. Often things are not what they seem to
Well, to quote him, "I managed to bend the crank shaft on my Craftsman lawn
mower." He seems to be pretty clear that there was an "incident" that bent
Sure but he should expect a charge for that if it isn't a warranty covered
Fine but again, he should expect a bill.
I agree that it is ok to provide only symptoms if he takes it there but it
would be morally wrong to NOT say, "I was mowing, heard a loud bang, motor
quit. When I lifted the mower, I found a boulder hidden in the thick
grass. It vibrated after I started it again."
Umm - whatever. The point of my post was to have Sears determine if they
would cover it (as someone else suggested). If you are looking for Morality
and are looking on the Internet for it your in for a rude surprise.
Unfortunately it's a dog eat dog world out there in the real world.
Take it a local auto parts store that has a machine shop. Quite often
the crank can be straightened on a jig if they have one in the shop.
Then get rid of this thing and buy a mower with a Briggs And Stratton
engine on it so the key shears before the cranks bends. Most of the
time the Sears mowere uses a Tecumseh engine with a hard steel key in the
flywheel that does NOT shear when you hit something. B&S uses a soft
aluminum key that will shear and thus cut out the engine by virtue of its
timing to the magneto.
email@example.com (Rich R) wrote in
FYI the key in the flywheel is there to prevent damage to the flywheel only.
Hitting rocks will still damage the crankshaft briggs or techumseh.
Do Not Straighten the crank. It has been weaken when you bent it and to
straighten it will weaking it some more. You will run the risk of it
breaking off while in use and flying out possibly causing injuring.
all rotary mower engines used alluminum keys with techumseh and
briggs. i've replaced and straightened hundreds of cranks in both
engines. it depends on where the impact occured as to whether the
You might wanna check with a well equipped mower shop. There used to be a tool
that was designed to straighten bent vertical-engine cranks in the engine. It
was a crude procedure as i recall but often worked well and saved a lotta money
on a rebuild.
I know it seems crude but the shafts can be straightened in the engine using
a dial indicator and a piece of pipe. The hardest part is holding the engine
to withstand the bending force applied by the pipe. Mine has been running
fine for a couple of years since straightening using this method.
The only special tool you will need is a flywheel puller, I usually
hold a block of wood on the top of the crank and hit it with a hammer
to remove the flywheel.
Find all the numbers you can on the engine cowling and take them
to a small engine place. They should be able to cross reference them to
the engine model and supply you with the correct crank. Buy a
mechanics handbook for you engine while you are there, about $10.00
iirc. Check the condition of the bearings before replacing anything,
the bent shaft could have trashed the bearings.
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