The blade on horizontal small engine lawnmowers acts as the flywheel.
It provides the inertia to keep the motor turning. It's almost
impossible to hand start the engine without the blade or if the blade is
loose and spins on the crankshaft. The small engines that don't use the
blade for the flywheel have a heavier flywheel. The aluminum key is
actually there only to align the flywheel on the shaft, the crankshaft
is tapered and the flywheel is held tight by the nut or starter mechanism.
The blade, if it's not bent and there is enough left to sharpen, then
sharpen and balance it. Don't worry about getting all the nicks out of
it. I usually use the body grinder when I sharpen one, using a file can
take a long time, always balance the blade. Ask the local mower shop
what they charge to sharpen a blade, and they will have replacement
blades and contrary to what the manual says you can usually get
replacement at many box stores that will work just fine. Make sure the
replacement is EXACTLY the same as the old one. There are 6 point star
holes and 4 point and square ones and diamond shaped ones and some have
three holes, mulching, non mulching and of course the proper length.
I'd stay away from the blades that use inserts to correct for the main
bolt hole size. The last blade I bought was made in France and needed
balancing even though it was brand new. The last trimmer string feed
bump head I bought was made in Italy and is a flimsy POS.
Have fun, tell your neighbors, friends, and co-workers you will take
their old mowers and weed trimmers, you should have a collection by the
end of summer to fix. Surprising how many of them just need a carb
cleaning, spark plug, starter rope, cable etc. and they are good for
another couple years. Some aren't worth fixing but many have a lot of
good hours left in them.
Oh yeah, speaking of cables, the one that pulls back the safety brake
and kills the engine when you release it, make sure it's in good shape
and pulls the safety brake completely back. It will cause a drag on the
engine if it doesn't and makes it hard to pull start.
It's a good hobby fixing old mowers and weed trimmers, keeps you in
shape pulling the starter ropes on those old dogs.
That's why you check to be sure your blade is tight. I spent many
hours on a mower learning *that* lesson. Finally broke down and
asked my neighbor to look at it.
First thing he looked at was the blade- 10 seconds and a big wrench
later I was good to go.
On Tue, 06 Jul 2010 06:36:54 -0700, Bob Villa wrote:
The flywheel contains a magnet that passes by a coil and induces a
voltage in the primary of the coil. Timing is crucial here and why a
motor wont start if the shear key has done its job after a blade
On Tue, 6 Jul 2010 14:01:30 +0000 (UTC), Chief Two Eagles
While you have the flywheel off, clean any surface rust from the
magnets and on the ignition. A fine sandpaper will work.
Once had a magnet fall out of the flywheel. Forget what I used to
secure it with. (Glue?)
cut the grass too the roots and go fishing
Yes that is true, I learned that in shop class back around 1970.
Engines with no direct mounted blade normally have a cast iron flywheel,
or some kind of flywheel with some weight to it. However, if the motor
is worn and doesn't have a lot of compresion, it will run with the blade
removed. And it'll scream like a 2 stroke! Did that as a kid with a
little 3 wheeled riding mower that was about shot. Wasn't worried if
the engine blew.
Only your grass will know the difference. It will be cut off cleanly rather
I wedge the blade still on the mower, and then use an ordinary socket and
ratchet to remove the bolt. I use a 6" bench grinder to put a new edge on
You'll find that all mower blades come balanced from the factory. That's
why you'll see odd corners cut off on the ends of the blades.
To re-balance a blade: Hammer a 3" nail into a stud so that it's parallel
with the ground. Hang the blade on the nail from its bolt hole, making sure
it's centered on the nail. Take note of which side is heavier, and grind a
corner down a bit on that side. Recheck and refine as necessary.
But not always. My current mower's blade was balanced by cutting off the
entire end of the blade, so one side is shorter than the other by about
Grind a TRAILING corner, by the way.
I use a disc-shaped stone meant for axes in order to lightly dress the
freshly-ground edges. You're not sharpening a butcher knife here, so the
edge you end up with just needs to be sharp enough to cause some pain when
you press your thumb into it, but it doesn't need to be so sharp that it
breaks the skin.
I just went and had a look at the nail I use for balancing, and it's a
1-1/4" finishing nail, not a 3".
And finally, UNPLUG electrical cord or spark plug before turning the mower
Cuts better. Briefly.
I don't do it as a matter of course, just if I happen to have to drop the
mowing deck for something else. And if you think blades are indestructible,
you should see mine after a season or two...not much left.
Yes, mostly tradition. A sharp blade cuts the grass easier, a dull
blade tends to beat the grass rather than slice it. I do my own
sharpening with a bench grinder.
Shears aparently lives on the residual income of off-spec parts. Their
mowers won't accept Briggs or Tecumseh parts in many cases, so you end
up going to Shears and buy their parts.
I sharpen mine every spring. Nothing cuts like a sharp blade. (that's
why) Dull blades just tear the grass. If you keep them sharp it doesn't
take long on the grinder. If you wait until it's blunt, it may take a
while to get the cutting angle planed and edge sharp again. Like any
other maintenance, let it slide and it's more work to get back into
shape. It also pays to clean up your lawn and remove the rocks. If you
never hit stuff it stays fairly sharp. I like a knife edge.
Interesting. The left side says to keep the blade sharp, the right side
says they don't recommend sharpening. Maybe they mean DIY versus a pro
doing the sharpening.
Sharp blades do cut better while the dull ones chop and tear the grass
apart. I happen to have a belt sander and it does a good job quickly.. A
grinding wheel is a bit harder to handle, a file works too. It does not
have to be perfect like a butcher knife, but it all helps. Take the same
number of passes on both sides to help keep it balanced.
I, personally, do not sharpen my blades. Never have. But if I were to do
it, I have about six tools that would do it without me having to remove the
visit my blog at http://cabgbypasssurgery.com watch for the book
I can't imagine paying someone to sharpen a blade. I sharpen our push
mower and the double blades on our garden tractor /mower and it
doesn't take that long. I do the serious sharpening with my bench
grinder, then dress them with a hand file. It probably takes more
time to dismount and remount the blades than to sharpen them.
By the way, if you are hitting rocks, stumps or such you might want to
clean up the yard a bit. One good "thunk" will bend the crankshaft,
and/or take out the lower bearing on most push mowers. Then you don't
have to worry about the blade :^)
I sharpen my own blade about once a season. A sharp mulching blade on my
Snapper cuts much cleaner, accurately and mulches much more effectively than
a dull one. It take me about 5 minutes remove blade, 5 to put in vice and
sharpen with a file and another 5 to replace. Have done this for at least
the last 25 years.
My walk-behind mower cuts more quietly with a sharp blade because the
governor calls for less throttle. It means fewer gas stops and a cooler
engine. A sharp blade produces less of the sticky pulp that tends to
build up and clog a mower.
If you pay somebody to sharpen it, you also have to take the blade to him.
Once I have a suitable wrench in my hand, removing the blade of a
walk-behind mower is very quick. I sharpen with a side grinder. I take
care not to overheat the edge, but I'm not sure if overheating will
leave the edge softer. I finish up with a big ceramic hone. After
installing a blade, I measure the height of a blade tip, rotate 180
degrees, and make sure the other tip is at the same height. Uneven
heights would mean vibration.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.