Totally off topic. Lawn mower troubleshooting

[hjfisk]

A back fire can shear a key .

[barnbiketom]

i pulled off the valve cover and and rotated the engine by hand. the valves are moving normally. if the exhaust valve was stuck open, the valve stem would not remain in contact with the rocker arm (except, of course, during valve overlap when the intake and exhaust valves are both fully closed).

I'm willing to bet it has a burned valve..

get a cheepo compression gage!!!

another possibility is a bad head gasket!!!

[bonanzadave]

Got a borescope ? Or a cheap dental camera ? Pull the plug and look at the piston. Hole ?

[barnbiketom]

The Key that we are speaking of is the FLYWHEEL MAGNETO KEY and has button to do with valve timing or compression... merely ignition timing.
Also. Some movers have no magneto.. so instead of confusing you.. I would rather know what motor it is etc.
You can't guess or just replace parts Willy Billy. Its easy to repair and diagnose correctly.

Check Co.pression with a Gage if it seems low.

And don't rule out a flooded condition making the rings cleaned of oil and no compression that way

[Dave_17954]

sounds to me like a sheared flywheel key. backfiring usually is a sign of bad timing. a possibly partially sheared key would make it back fire and now a no start means a completely sheared flywheel key. What happens is it would still fire under a partial shear but not all of the fuel would be burnt and and some would get dumped into the exhaust which would then cause it to explode/backfire. A backfire can cause a shear to the key and I did have a neighbor shear his key on a rider when just mowing. its the same reason anti-fire selonoids were installed on the bowls of carbs. when you turn off the key you turn off the electrical power to the engine but what still happens if you shut it off at high speed is the piston would still have compression pulling fuel into the cylinder and then pushing it out into the muffler. raw gas and hot muffler equals a big boom and I'm sure we all been there done that

[DanTheMan]

I've had three B&S engines (two of them 16-18 hp) of the flathead variety (valves in the block) wherin the valve seat, either the intake or exhaust dislodged from it's cavity. I removed the head, put the seat back in and peened it in with a center punch. It's a common B&S problem, one of my friends in the lawn care business told me it's happened many times to him.

[Bigred0216]

It wound up being a sheared flywheel key. I am going to do a valve adjustment and an oil change and sharpen the blades while i am at it so i wont have to mess with it again this season. Now i need to track down my puller and a cheap socket to get the flywheel off. Grass aint growing yet so i still have a little time. Thanks for all the help everyone :-)

[recycled64]

It wound up being a sheared flywheel key. I am going to do a valve adjustment and an oil change and sharpen the blades while i am at it so i wont have to mess with it again this season. Now i need to track down my puller and a cheap socket to get the flywheel off. Grass aint growing yet so i still have a little time. Thanks for all the help everyone :-)

You're welcome

[Dave_17954]

I used to be a certified B&S repair person. Glad you got it figured out. Them briggs usually run forever......

[Bigred0216]

Well I thought I had it figured out. it has spark, compression, and it is in time. It is getting fuel, but I am not sure if the carb is adjusted properly. I guess I need to get the adjustmetn specs for the carb.