how do u know its bent shaft?

Discussion in 'Lawn Mowing' started by SERRICO, Jul 2, 2004.


    SERRICO LawnSite Member
    from TX
    Messages: 94

    I have honda 21" lawnmower with dual blade for mulching.
    Reasonly, I noticed that cutting quality is down even with new blades.
    Is there any way to test to see if shaft is bent or not?
  2. chuckers

    chuckers LawnSite Senior Member
    Messages: 657

    it was answered before in the repair forum like 2 days ago
  3. mbricker

    mbricker LawnSite Senior Member
    Messages: 505

    You are referring to the engine crankshaft, I presume.

    Pull the spark plug wire off the spark plug.


    Stand the mower up whichever direction does not drain oil out the breather. Use a c-clamp, duct tape, vise grips, or whatever to firmly clamp a ruler of some kind from the edge of the deck to where the end just touches the shaft. It may be easier to remove blades first. Manually rotate the shaft. Look for a gap between the shaft and the end of the ruler to grow larger then smaller as the shaft turns thru one rotation. If the gap is growing larger then smaller, you have a bent shaft. If there does not appear to be any difference in distance from shaft to ruler thru a full rotation of the shaft, the shaft could still be bent but probably not enough to affect your cut.

    The proper and hi-tech way of checking this would be with a dial indicator. What you are checking for is called "run-out."

    The cure for a bent shaft: If it's a nice mower replace the shaft. If the mower is a near junker anyway... I actually once bent a shaft so bad the mower would not run--binding too much. I whacked it with a LARGE hammer and got another 4 years homeowner use out of the mower.

    BTW, if you haven't hit anything with the blades, I doubt there is anyway the shaft could get bent. Decreased quality of cut can be directly related to a buildup of crap on the underside of the deck. You ARE keeping the deck cleaned out, aren't you?
  4. chuckers

    chuckers LawnSite Senior Member
    Messages: 657

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