Vibrating push mower

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Hi all, my 2008 craftsman push-mower is vibrating badly. The blade is new and on tight, and the oil is new and perfectly filled. What could be causing this? It is so bad it is unuseable.

Also, I know I'm a small engine mechanic, but I have had so much stress lately over someone I am overloaded and can't think.

Thanks,
TB
 
Just because the blade is new doesn't mean that it is balanced.

1. Take the blade off.

2. Drive a nail into a stud at a 90 degree angle

3. Balance the blade using that nail by using a grinder and taking a little off of the end that falls while on the nail.

4. Put the blade back on and tighten the bolt snugly.

5. Still have a problem? Take it back to Sears and get them to look at it.
 
Originally Posted By: Steve S
Take the blade off and start it, see what happens then go from there.


No No No....have someone you dislike start it with the blade off because you will injure yourself doing that. Trust me I found out the hard way.
 
Troy Built, I too think it's likely to be something with the blade ... possibly balance ... though that's gonna have to be severe to make the machine instantly unusable.

I put on a blade once, got it good and tight ... but the spacer moved out of place as I tightened it and so it was on slightly crooked and did just what you described. This was not easy to tell ... until I got on my knees and looked at the blade horizontally.

I'd take the blade off, check for balance as described above then put it back on VERY carefully making sure all shims & spaces are where they should be.
 
I just came back from pulling the blade from my 1998 Craftsman it has a Techumse engine. It sure runs quiet without the blade ,smoother as well
 
Most likely, as others have mentioned, a unbalanced blade, i like to put them on a screwdriver as i sharpen them to balance it out. (hold handle, place blade center hole over driver tip, observe balance)

Also possible that your shaft is bent, but you would remember hitting something with it. You may also have a partially sheared key-way in the flywheel or blade adapter.

Make sure you put the blade on in the correct direction. (happens a lot) Muncher or split blade types placed on backwards can also cause vibrations, as well as sucking big time at mulching and creating vacuum. I don't know why this causes vibes, but it does.

Be safe! Lawnmower accidents are common and typically result in a lost limb or digit. Un plug the spark plug!

As far as operating without a blade goes, it's fine, it just usually has a significant kick-back when pull starting due tot he reduction in rotating mass to absorb the rapid revolution changes.
 
Originally Posted By: TrentMiller


As far as operating without a blade goes, it's fine, it just usually has a significant kick-back when pull starting due tot he reduction in rotating mass to absorb the rapid revolution changes.
I don't know where some ideas come from.
 
If it's bent a little, you can straighten it. If you take it to a dealer, they likely won't touch it with a ten foot pole for liability reasons. Don't let anyone heat it up with a torch because it might change it's temper and make it dangerous. Let me know and I'll walk you through my totally scientific, high-tech method of straightening a small engine's shaft. That sounded gay.
 
Flip the blade around the other way. Mine is slighty off-balance. If it is on one way, it vibrates alot, but if I flip it around facing the other way in relation to the mount, it runs smoothly. I think it offsets the vibration from the engine or something like that.
 
I like Trent's suggestion on a partially sheared key-way, I had the same thing happen to me after I hit a partially burried fuel oil tank cap while mowing at an unfamilar yard.
 
Originally Posted By: Jason Adcock
So...any news on the vibrator??


I don't need a vibrator!


Oh, I see you ment my pushmower! Well, the blade, for what I can tell, is perfectly balanced. It has new oil, filled correctly. The Blade is new and on as tight as possible. I have noticed that the vibrating starts after it has warmed up. when it is first started, there isn't any. Could the engine be loose on the body?
 
Run the engine to warm it up then shut it down.
Take the blade off, find a long bolt that will fit in the center hole(if it has one) of the crankshaft and use it for leverage. See if you can wiggle the crankshaft. If you can, the crankshaft bushing/bearing might be worn.
 
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