Flywheel keys keep going and going out of time

Your 17.5 is out of time. The key in the flywheel slot is most likely kicked sideways and let the flywheel go out of position and it will do just what it is doing now. Remove the flywheel and check the timing key in the slot and you'll see it's either shifted or bent a slight amount. Replace the key and back together. Starts like a new one.

Take the cover off the housing that covers the flywheel. The crank shaft comes up the middle of the flywheel and has a slot in the end. The slot has the woodruff key in it. The key fits in the slot on the flywheel. When you hit something with the blades the crankshaft stops and the flywheel keeps turning. This shears off the woodruff key or makes it move out of position and then the timing becomes out of spec. The motor wont start. You need to pull the flywheel off and replace the woodruff key. They key looks like a half moon piece of metal.

The timing on any two-stroke engine is dependent on the condition of the key (small square metal piece) between the flywheel and the drive shaft. (it keeps the flywheel from rotating on the driveshaft.) If you believe that your timing is off, you must remove the flywheel from the driveshaft and check the condition of the key. if the key is not perfectly square, it needs to be replaced. Damage to the key occurs when the saw blade has been stopped suddenly (like when you hit a chain link fence with the blade, or when the chain comes off of the bar while cutting).

Sounds like it could be a broken flywheel key and your engine is slightly out of time. You will need to remove the flywheel and check the key and replace it. The key is only a small block of aluminum but keeps the flywheel in proper time with the crankshaft. Part costs a couple of bucks from Sears or any small engine shop. It is a pretty common part.

I believe your problem is not the coil/magneto but rather your timing. If you hit something hard with the blade you most probably sheared the timing key. This key is what keeps your flywheel in the proper timing position.
Remove cover top of engine, remove flywheel bolt,remove flywheel, remove key. If key is sheared off or even dented replace.Put back together. Happy mowering.

The engine flywheel key is probably sheared, throwing the timing off and producing the soot. Remove the engine cover and starter cup on top of crankshaft. Look down the side of the shaft where the flywheel is held on. There is a long slot in the crankshaft there that runs vertically. Observe closely, and you will probably find that the slot in the flywheel has moved AWAY from the slot in the crankshaft. The key holds the two together, keeping the engine in time. The key is aluminum and a 1 dollar part. You will need to remove the flywheel to remove the old key, clean the slotted area up with emory cloth, and reinstall a NEW key. Timing will be restored and no more sooting!

He more than likely sheered the key in the crankshaft. When the key bends or breaks it throws the timing off and the engine will not start. The key is there to prevent damage to the crankshaft when you hit an object. You will need to remove the engine cover and then use a puller to remove the flywheel. Where the flywheel connects to the crankshaft you will see the key which is either broken or bent. All you do is buy a new one and replace it.

hi,

first try a new plug, make sure you get the right one. did you recently hit something hard in the yard? you may have snapped the flywheel key. its under the cover and then its under the mesh grille on the flywheel. under the big nut on the flywheel is the flywheel key. it keeps the flywheel in time with the driveshaft. they are made to shear off if you hit something extremely hard and will throw it out of time. if it wont start with a new plug and starting fluid then it may need a new flywheel key pin. make sure you always run your lawnmower out of gas at the end of the season so the gas doesent turn to varnish too..

jm

If the flywheel key keeps shearing off, you may be putting it together wrong. I put the flywheel on first and then insert the flywheel key. The surface between the crankshaft and flywheel may be too polished from years of use. I put a little bit of valve grinding compound on the crankshaft where the flywheel is going to sit and then I use an air wrench to tighten the flywheel nut. HTH
Good Day.

When you the key this time, put the flywheel on first then the key but this time use a little grit between the flywheel and crankshaft. Something like grinding compound. It will keep the flywheel from moving plus make sure you torque down the flywheel nut good.
HTH
Good Day.