Two things make a flywheel key shear, usually!

1. Loose flywheel nut! Tighten up TIGHT, + a 1/4 turn, or as tight as you can make it! Hold flywheel with screw-driver in the fins, or use a leather belt wrapped around the flywheel!
2. Hitting something with the blade! Solution?: don't hit things with the blades! Pick up all rocks, sticks, dog bones, toys, gravel, and mark the curb boxes for the water and natural gas connections, with red or blue paint!

Rusty, excellent idea about using a leather belt to hold the flywheel while torquing nut.(won't damage flywheel and negates the use of a piston stop which I am not crazy about). I think there is a tool called a strap wrench, works like a oil filter wrench only uses a belt, but I don't think it's leather. I know how much grip a leather belt has. I once worked on machines that used leather in the clutches.Tremendous grabbing power!If I can't find a suitable strap wrench I am going to make one using a leather belt. Thanks.

"mark the curb boxes for the water and natural gas connections, with red or blue paint!"

Blue is right for water, but yellow is the recognized marking color for gas. Watch out for sewer cleanouts too.

While the flywheel nut needs to be torqued properly, to prevent key shearing, "Hold flywheel with screw-driver in the fins" is the worst possible advice. You are guaranteed to break off fins and unbalance the flywheel. Guy who suggested this must have a business selling replacement flywheels.

A strap wrench can be a good way of holding flywheel, although most strap wrenches aren't big (long) enough to accomodate a typical flywheel. Also, since most engines on rotary mowers use a "zone start", you would have to remove the flywheel brake mechanism to use a strap wrench. That said, Snap-On makes a very good strap wrench. I have one I use to remove the oil filter on my Powerstroke.

The right way to remove flywheel nut or starter clutch is to get the right tools. Briggs sells a wrench for the flywheel and also for the starter clutch. Cost about $30.00 and 12.00 respectively. I believe Tecumseh and others have similar flywheel tools. The URL for Jack's shows the type of tools for Briggs. Even if you only use it once or twice, they are a good investment.

Here is a link that might be useful: Flywheel Tools, Jack's Small Engine

I learned the hard way about overtightening a flywheel nut. I "assumed" the torque was about 35 ft. lbs and split the aluminum flywheel. Went to the book and it was supposed to be 23 ft. lbs, or so. Cost me about $100 because it was electric start.

Don't feel bad, baymee....I saw a young, freshly hired "mechanic" using an impact wrench to tighten a flywheel. He did not last very long, to say the least!

Give a man a fish, feed him for a day, teach a man to fish, feed him for life!

On the other end of the crank, I think too many people use an uncontrolled impact to tighten the blade. I always Lubriplate and tighten the bolt or nut by hand.

I use an impact wrench on both the flywheel and blade
fasteners and have never had any problem. Of course,
an impact can do some serious damage in the hands of a
moron.

This site has changed quite a bit, as advertising, and
promoting other websites would have gotten a member banned.

Fish

>promoting other websites would have gotten a member banned.

Checked out that other site and found valve setting instructions incorrect.

Walt Conner

I just bookmarked bikini of the day.

I haven't checked out any other stuff there, once I found
out that this thread is just an info-mercial for that
site, and this guy's business, which is prohibited.

Spike would have put the smackdown on it quick!

Fish

Aww, c'mon, fellers!! A guy shouldn't have to buy a $30 flywheel wrench just to tighten his home owners lawn mower flywheel! And, a screw driver in a flywheel is only a last minute thing! And, the rope in the spark plug hole is good!!
And, if you don't stick something in the fins, or use a strap, an impact wrench does the job o.k.! just spin the nut on, and it'll be tight. I only use it on the larger engines, though.
One nice thing about these sites--you can pick somebody's ideas apart, and make somebody appear to be a nut, without the danger of getting socked in the nose! Ain't it great? Whoo-hoo!
Rustyj

After tilling gardens for 20 years, my TroyBilt became due for a new starter clutch. I put one in, pulled the cord, and before I could even put it in gear, it sheared the key, I replaced the key... and it sheared again. So then I went to the computer, Googled "Flywheel Key shearing" and of course this Forum subject came up at the top of the list.

I put another key in---only this time I tightened up that starter clutch good and tight!

Just tilled up the whole garden. Thanks guys!

-------

Now we know why Briggs puts a whole bunch of those keys in a package...

"I put another key in---only this time I tightened up that starter clutch good and tight!"

Well there is such a thing as a torque wrench and torque specifications. Torques for B&S engines between 12 and 20 hp will run from 65 lbs to 150 lbs. and for a reason.

Walt Conner

What is the flywheel? Getting confused as to how to repair my mower with the vibrating.

for rotary mowers anyway.
Clamp a large pair of vise grips, "C" clamp or other similar devise to the bottom of the deck in a manner which allows the blade to jam against it.

And as Fish said, I too have used a impact gun for over a quarter century with no problems. Impact guns do have a power setting on them. You can take a 200 ft lbs torque wrench and not pay attention to the guage and do damage as well. Some folks can destroy a Sherman tank with a tooth pick.

Blocking the blade is the easiest and safest way to tighten the flywheel nut. I just stick a 2x4 in the discharge port, catch the blade just right and finish the job. The torque required for the flywheel nut is not sufficient to bend the crank or blade. BTW, make sure to pull and ground the plug wire before ever turning the engine by hand or with a tool. I use the same wood block when tightening the blade.

To: Lilibet 2000! If you can't see the flywheel on yer engine, i think you had better not try to repair the machine!
And, if you have vibrations in the mower, you probably have a bent blade, which is that thing under the mower deck, that spins around and cuts the grass off, and which will do the same fer yer fingers, if you are foolish enough to lift the machine up while it is running!
So, that being said, do this: Turn machine onto its side, with the carburetor to the up side, muffler down. Pull off spark plug wire and tie it back away from the spark plug. Then, using a piece of rope, or masking tape, tie back the thinn wire thing on the handle, called a blade brake, that you pull back to start the engine.
With that all done, turn the mower blade, and measure where the blade tips are close to the edge of the deck. You may find one end closer to the ground (relative to being in operating position) than the other end, which will indicate that you have a bent mower blade. This usually means replacement! Ther is a bolt holding the blade on, some models have 2, but you must remove the bolt to replace the blade. Make sure, if you do that, you have the sharp edge on the lower side closest to the grass. If you get it on upside down, instead of cutting the grass off, it will put it on!
If this info confuses you, better pay somebody to check it out, and fix the problem. Get a price before giving the OK to fix it!

dont even put a key in. just make sure the the groove is lined up and tighten it with an impact. it works just as good.ust make sure it is really tight this is what i do on my racing motors if the key shears.

I've replaced the flywheel key 2 time and eveytime the mower cranks its just breaks again?