Lawnmower help needed!

[Grim/Don]

Was mowing this weekend and everything was going fine and then... The mower starts reving. Hign and low. High and low. If I tried to mow with it, it would die.

Tonight I replaced the oil, air filter and a very black spark plug. Same thing. Starts up in the first pull and runs great for about two seconds, then the high and low thing. Checked the plug again and it was black.

I was thinking that it's the carbuerator(sp?), but there's no way to adjust that with this mower (Murray 4.0 hp 22 inch). I called a buddy who's pretty mechanically inclined and he said (from my description) that he thought it sounded like there was something caught in the gas line. Which would seem possible to me, as it acts like it's choking out on me.

Any advice?

Thanks for reading!

 

[Mike G]

I'm betting you hit something while you were mowing, and partially sheared the flywheel key. Very common, as the keys are made of aluminum. Saves tearing up an expensive crankshaft. You can check this by removing the top cover, and looking down the keyway. If the keyway on the shaft doesn't match the keyway on the flywheel, you've sheared it, and need to replace it.

Get a book on your engine type, and a couple of flywheel keys, and replace it.
Books and keys are available at The Home Depot, Lowes, and Wal-Mart may also have both. Any small engine place near you will also have these, but they'll want to do the job for you, and that will cost you plenty.

If you are mechanically inclined, you should have this done in about 30 minutes, if you follow the procedures in the manual.

Email me if you have any other questions. I have a vast amount of experience in repairing small engines, and will be happy to help further if needed.

 

[Robbie Roberson]

Grim/Don, check your gas cap, loosen it and start it and see if it runs, if it does, tighten gas cap down and see if it still runs. If not, then you need to clean the air hole in the cap. If this does not work, get a hand pump used for kerosene or similar and pump out tank aroung gas line to see if you have blockage or water in tank.
It could also be the needle valve or something in the float hanging it open and flooding it, do you smell heavy gas oder ? Sometimes you can shake the lawnmower a little and un-clog or un-stick the float.
The black plug leads me to think it is maybe not firing right either, how about your gap in plug ?

Robbie Roberson

 

[carpediem]

Check the gasket between the carburetor and the manifold, and from cylinder to the head. You can use a spray bottle with water. Start the engine and spray a heavy mist where the gaskets are, if you notice a change in rpm you have your leaky gasket. Good luck. Let us know how what you find.