Sears B&S engine FLYWHEEL KEY loose in grooves will the NUT be enough to keep it work

[drcwks]

Sears B&S engine FLYWHEEL KEY loose in grooves will the NUT be enough to keep it work

I have a SEARS self-propelled lawn mower model 917.377240. It has a B&S 7 hp OHV engine.

I just sheared the flywheel key I found out after disassembling everything. The flywheel groove isn’t as dominant on the bottom. Almost like it was tapered from the top but I’m assuming it was due to the key moving and wedging into the crankshaft threads.

I had to drill the key out and didn’t really hit the threads and that relieved the pressure so I could remove the flywheel. A gear puller didn’t work until I relieved the wedged key.

ANYWAY. I’m putting it back together and the slot on the crank was a little messed up. I took A file and dressed it down. LONG story short. When I put the flywheel back on the shaft and put the key in, there is a little play in rotation. NOT much but the key almost DROPPED into the grooves. Pushed in with my finger.

My question is….. Do they make an over sized key by about .003 or so? The key I have measures .558 long by .183 width and by .142 depth. A new flywheel costs $136 and I’m not sure the crankshaft slot isn’t part of the tolerance problem too, so replacing both is not an option.

Let’s say I use the key to clock the flywheel. Is the tightened nut enough to keep the flywheel from rotating back and forth on the crankshaft to eventually have the key fail or will it take hitting another stump to get the flywheel out of timing? What about an additional nut?

Sorry for the novice terms but this is the first time I’ve tried to repair a lawn mower. I usually just put it in my driveway with a FREE sign and it’s gone in no time.

Thanks in advance,
Dean

 

[mechanic mark]

Re: Sears B&S engine FLYWHEEL KEY loose in grooves will the NUT be enough to keep it

https://www.searspartsdirect.com/mo...aftsman-917377240-gas-walk-behind-mower-parts

try taking crankshaft with loose key to small engine repair shop asking for larger key to fit.

 

[Tinkerer200]

Re: Sears B&S engine FLYWHEEL KEY loose in grooves will the NUT be enough to keep it

Flywheel key is intended for initial alignment only. The taper and proper torque of flywheel nut hold flywheel. It is unfortunate that B&S started using hard keys on some engines after decades of using soft keys which would have prevented damaging the crankshaft.
Larger key will only work IF key way in flywheel is enlarged same as crankshaft, doubt it.

Walt Conner

 

[bertsmobile1]

Re: Sears B&S engine FLYWHEEL KEY loose in grooves will the NUT be enough to keep it

If there is enough good groove you can build up the keyway with Devcon.
There is a different one for steel & alloy.
Follow the instructions 100% and it should hold as the keyway is constrained and should not be under any load if the nut is done up tight.
If there is evidence of the flywheel spinning on the crankshaft then apply a LITTLE Brasso to the crankshaft and use it to lap the flywheel to the crank.
make sure you wash it all off course it is abrasive & will not do the top oil seal any good.
Once the shaft & flywheel are both polished sort of dull, they should lock in really tight when the nut is tightened down.
If there is a welt raised on the edge, file that off before you start.