Loose flywheel?

rustyj14(W/PA)October 30, 2013

A friend called and asked me to look at his lawn tractor engine, an OHV Briggs, around 12 h.p., so i went.
He said he couldn't keep the flywheel key from shearing. I looked at it, and sure enough the key was sheared. He said he used 3 keys, and each one sheared right away! The flywheel nut didn't have any kind of locking washer under it, and he said it didn't need one! I even tightened the nut, using his hand operated, 1/2 in. drive torque wrench, but as soon as it starts, right away the key shears. I think he is wrong about the locking washer, but i said i'd ask here.
The engine turns easily with the starter. And it even ran a bit, but without the locking washer, it sheared the key. When it started, the engine sounded ok-no rattles, or thumps. Also, this machine looks like it has sat outside, uncovered, for most of its life! Never blown off, or squirted, or any maintenance. The machine came as a gift, and my friend wants to get it going. The P.O. said he installed a new battery in it, yes--around 5 years or more, ago. A sad looking piece, it is. And, yes, i know about squirting them off with the garden hose---but this is an extreme case of dirt! Any help welcome.
Rusty Jones

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mownie(7)

Well, if the nut is the correct nut of the "flange nut" type (looks like a nut with a flat washer made into it) then it does not use a lock washer. The wide base of the flange area spreads out the contact over a large enough area that it has tremendous holding ability.
But, it is critical that only a genuine Briggs brand key be used and there has been some recent changes made by Briggs regarding the key and the torque value for tightening the nut.
Tomplum can help me out if I err, but I think there has been issued a new key (black color) for these engines and the torque has been raised up to 110 foot pounds instead of the old 100 Ft Lb value.
It is just as important in how/when you insert the key as the other factors.
First off, the flywheel bore and the crankshaft taper must be absolutely clean and free from any oil, grease, or dirt. Solvent wipe if needed using clean rags.
Second, place the flywheel onto the crankshaft and align the keyways.
Third, insert the key into the aligned keyways and gently tap it down flush with the surface of the flywheel. Tighten nut to 110 foot pounds.

    Bookmark   October 31, 2013 at 12:36AM
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tomplum

Yes. The new key is PN 796335. No fine crack at the key way in the flywheel?

    Bookmark   October 31, 2013 at 11:33AM
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rcbe(6)

Tom raises a good point on the fineline cracks, Rusty... yer eyes are prolly gettin like mine - a little blurry on the closeup stuff - get thet big magnifying glass and yer best flashlite fo a visual onceover - if any bad indications, get a rattlecan of crack chk/developer and spray 'er down.... if they is fine hairline cracks anywhere around that keyway groove, they will show up like interstate roads on a rand-mcnally map.....

    Bookmark   October 31, 2013 at 2:30PM
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rustyj14(W/PA)

Well, i called the friend, and went there. He had it running. He used his calibrated torque wrench, and tightened it correctly, and it runs.
the owner was there. He was complaining about the "crappy" Briggs engine, and how it was a piece of junk, and all that! I told him, from the sounds of the mis-treated engine--that he ought to be glad it runs like it does. I think he wasn't impressed by my comments, but--as they say--the truth hurts! I offered him $50 for the tractor, but he refused to sell it. I think he wants to torture it some more.

    Bookmark   October 31, 2013 at 7:39PM
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tomplum

Must have been the bubble gum hadn't dried yet!

    Bookmark   November 1, 2013 at 1:09PM
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