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Re: [Shop-talk] Lawn mower engine & blade question

To: shop-talk@autox.team.net, Wayne <wmc_st@xxiii.com>
Subject: Re: [Shop-talk] Lawn mower engine & blade question
From: Pat Horne <pat@hornesystemstx.com>
Date: Fri, 16 Jul 2010 17:56:43 -0500
  Wayne,

There is a good chance that you damaged the engine

  I wouldn't start it without the blade, the it does act as a flywheel, 
and the engine could overspeed easily without one installed. There are 
several checks you can do though. First, remove the spark plug and 
slowly turn the engine through a full 360 deg by hand. Are there any 
tight spots? You will have more drag when the crank to connecting rod 
are at 90 deg to each other. Next, tip the mower up and look at the end 
of the crank while you turn the engine over. The shaft should stay 
centered and not wobble. Usually the crank will get bent when hitting 
something like this. If it isn't bent and not dragging, put a new blade 
on and give it a try. If it is bent, there is an old method of 
straightening the crank that I've seen done, but never used that may 
work for you. Find a piece of steel pipe that will slide over the crank 
and bend it back to where the end of the crank does not wobble. There is 
no guarantee that it will work for long after straightening, but if you 
want to take the chance, you can't wreck it any more than it is. I've 
never heard of a crank breaking after being straightening, but I suppose 
it is possible, so use it at your own risk. Now, back to your first 
question. If everything seems OK you can block the butterfly so that the 
engine won't try to run at full speed and try to start it, but only for 
a short test.

Peace,
Pat

Thusly spake Wayne, On 7/16/2010 4:57 PM:
> Hi Guys,
> I have a simple MTD push lawn mower (that I use to mow around my shop) 
> with a B&S engine and 22" blade.  Today I nailed a small tree stump 
> with it.  Usually you just "graze" things and it somehow survives when 
> you lift off it.  Not this time.  The engine stopped instantly.  The 
> tip of the blade, about 3" back, is bent 90 degrees downward!
>
> Is there any chance I damaged the engine?  Is it ok to start it with 
> the blade off, just to see if it runs ok?  (don't know if it depends 
> on the blade as a flywheel, or needs it as a load.)
>
> -Thanks, Wayne
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-- 
Pat Horne, Owner, Horne Systems
(512) 797-7501 Voice            5026 FM 2001
Pat@HorneSystemsTx.com  Lockhart, TX 78644-4443
www.hornesystemstx.com
-- We support Habitat for Humanity - a hand UP, not a hand OUT --
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