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Straightening crank on small lawnmower

1351 Views 9 Replies 7 Participants Last post by  mla2ofus
How many times would you dare to do it before it broke?
How do you do it?
Just want to see what your technique is. :thanku:
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Can't. Bent crank, means junk motor. Try bending it back and will get off balanced and distinegrate the motor internally.
Strangely enough, bent cranks and cams on multi cyl engines are straightened in a press at time of manufacture, before final machining. it is a very precise process using a line up of dial indicators.

The odds on you getting it right in your garage at home are low and still it should be magna fluxed afterwards for cracks. Just not worth the risk.

Are you sure the crank is bent and not just the blade itself?
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Cranks are bent due to impact loading when the mower blade comes in contact with something that is reluctant to move.

When impact bends, impact will also straighten. It takes a very judicious and accurate impact with a sledge hammer to apply the correct amount of force in the correct direction.

You'll have about the same odds as winning the Lotto Max to get it right, and you will still have to magnaflux or Zyglo the crank for cracks after dialing it in.

Replace it, and then experiment with the hammer. It's junk anyway.
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The first shop I worked at had a jig with a dial indicator and a bolt that was pressed against the end of the shaft. I used it many times, never had a subsequent failure that I knew of, but would not take the chance now. Short block or replacement engine is the way to go, most times replacing the crank and possibly the sump is not cost effective.
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There ya go............:sidelaugh
Yea pretty much the same way except I take the blade off & mark the high spot.
Get a piece of heavy wall pipe & wack away.
I know it's not right but ya gotta have a beater mower for rough stuff.
Done it on this one about 3 times so far.
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3 TIMES ??? I sincerely hope nobody gets more than a good scare when it finally lets go.
Dial indicator is best to use w/ the pipe and hammer.
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