Mower runs, but vibration is too intense


Old 06-02-07, 11:31 AM
Thread Starter
Join Date: Jun 2007
Posts: 1
Question Mower runs, but vibration is too intense

Hello all,

I have a Yard Machines 4.5hp 21" rear bag push mower. Last weekend I was mowing my lawn when my mower blade hit a large (buried) rock. The blade became too warped to be used again (even after reshaping), so I replaced it. Since summertime is here, and grass seems to love the sun =), this weekend I had to mow my lawn again.

I started the mower and for about 3 seconds it ran fine. After that white smoke began to spew out of the exhaust (yes, we have oil here) and the mower began to vibrate very strongly. For perspective, the mower also sounded about 3 times louder than usual. I shut it down, then cleaned the exhaust. I also found that my air filter (the sponge in the compartment above my fuel tank) had what seemed like oil in it.

So, I'm assuming that the motor is running dirty. Can anyone please offer some advice on what I should do to fix this? I know that this whole problem was probably brought on by tipping the mower over to replace the blade (and yes, I know that I'm an idiot for doing this), but I should be able to clean the carburetor and get the motor to run true right? Will the fix be worth it in the end?

Any help would be greatly appreciated, since I can't afford to buy a new mower right now. Thanks!
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Old 06-02-07, 05:53 PM
msidan's Avatar
Join Date: Apr 2006
Location: Gouverneur
Posts: 289
You should change the oil to begin with. But the vibration is probably coming from a bent shaft as a result of hitting that rock. If this is the case, then it's really not worth putting money into.
Old 06-02-07, 06:32 PM
puey61's Avatar
Join Date: Apr 2004
Location: Upstate New York
Posts: 3,224
The smoking is likely related to you tipping the mower over to inspect/service the blade. You likely tipped the mower over well past the point you should have and now have oil in the combustion chamber as well as the muffler. Spark plug or muffler side up and no more than a 45 degree angle is the proper way to tip. If this is the case, the smoking will disipate in a short period of time, just be sure to check the oil level since you have now burned some off. But, again, as Msidan pointed out, it may not be worth any more time or effort if the crankshaft is bent severely, as it appears to be. Furthermore, you have likely sheared the flywheel (ignition timing) key and even if you want to deal with the vibration, you would have to replace the key to get the engine to run respectably.

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