What kind of job is it to replace the flywheel key on a 4 H.P. engine?

Question

My lawnmower hit a piece of lumber hiding in the deep grass & it stopped the blade suddenly. Now it has no power & dies frequently & adjusting the needle valve does no good. I'm told it might have sheared the key. There is a man who has a shop on wheels, but he charges $60 just to come out to the house. Would you say it is an 'easy', 'medium', or a 'big job'?

Answer 1

A flywheel key is a simple job if you are mechanicly inclined, and more difficult if you wonder what a rachet looks like!
The flywheel key could be the problem. However I would check the crankshaft. It could be bent, causing the mower to run rough, vibrate excessively and die. To check the crankshaft remove the spark plug, tip the mower up **With the carb on the upper side**
Pull the rope and see if the bolt in the center of the blade stays true in the center, or wobbles. (it is easier to have someone else look for you, but not too close!)

Answer 2

Its a fairly easy job, with the right tools - the guy is most likely right - the main purpose of the flywheel key is to protect the motor.
Years ago i made up a flywheel puller for Briggs and Stratton motors - on these motors theres 2 pre drilled and threaded holes on both sides of the main flywheel hole. It consists of 2 pieces of 90 degree steel angle around 6 " long welded together in a ' U' shape- 3 holes are drilled - corresponding to the holes in the flywheel, a large nut welded to the center hole ( crank end) , and two smaller nuts welded to the smaller holes, 2 long bolts thread thru the side holes and a rather long large bolt for the center- a beefy one.
You can buy one for your type of motor at a tractor parts store, but i made this since i tinker and had a welder.

Okay- to remove the flywheel cover, theres a few bolts holding it down, you'll need to remove those - if you think you might have any reassembly issues, take pics or make a drawing of how it looks before taking it apart.
The flywheel is the large round finned 'disc' on top of the motor, you might want to loosen the magneto ( that runs the spark plug spark ) to have some clearance.
I use a 'C clamp ' under the flywheel and between a fin- threaded up and against the engine block to keep it from spinning.
Use a socket and a breaker bar to remove the nut holding the flywheel on ( its tight) - under that youll see the flywheel key/ keyway slot on both the flywheel and crank end - if they arent lined up, then it needs replacing ( not too expensive at tractor parts).
Attach the puller to the flywheel, after spraying the center with some PB blaster or WD 40 - and let it soak a bit.
Now, line up the center bolt and carefully tighten on the end of the crank- this is the part thatll scare y - when it comes off, it comes off with a "BANG" - as its a press fit- its fine.
Clean the top of the motor/crank end/ flywheel center, use a very lite coating of never seize on the crank end/threads on crank, and inside the flywheel center hole - helps it come off easier the next time ( if need be).
Insert the flywheel key into the key way, and gently line up and set the flywheel back down, put the nut back on- thats how you 'press fit ' it back on. Me i just tighten the nut as much as possible, should be enough.
To adjust the magneto, use a thin piece of cardbord, like from an oil filter box, between the magneto and flywheel, line up the magnet on the flywheel ( usually the rivited part on the flywheel) and the magneto, and make sure the bolts holding the magneto are loose- itll snap right tight to the flywheel. Tighten the magneto down, and remove the cardbord.
Reassemble the rest of the mower and see if itll run ( it should).
On a scale of 10 being a difficult job- id say its a 4, with the right tools. Do not bang on the end of the crank with a hammer, Do not pry on the flywheel, its just cast iron and can break easily.
Kidd

Answer 3

bologna to flywheel remedies. the key they were talking about on the flywheel has nothing to do with the running of the engine. the flywell only cools the engine when running. |The other key for engine timing is located on the shaft of the engine in the crankcase and is a major job to replace.

Answer 4

fairly easy, remove the cover over flywheel, remove the nut that holds the flywheel on if you have a wheel or gear puller use that to pull the F-wheel off, if not I leave the nut on the shaft flush with the top of the threads, and pry up put
[ pressure] on one edge of F-wheel with a small pry bar, [don,t try to pry it off,] place a pc of wood on nut smack the wood with a rubber mallet, to break the seal of the F-wheel,
replace key way and F-wheel tighten nut,