Sudden onset of vibration

I looked around to see if I could find any one with a similar issue, and found this was a good forum with other lawnboy users. I hope you can help me diagnose the problem.

I have a Lawnboy model 10424, it is from the late 90s or early 2000s. I was mowing the lawn, and I felt and heard something, then the whole thing started to vibrate so much, the three screws holding the plastic cover on top came out. At first I thought maybe the screws just worked their way loose over the years and fell out. I found replacement screws in my stash of screws and started the mower again, and the same thing happened. I turned the mower over, thinking it was unbalanced from breaking the blade or something. I found a chunk missing from the deck, but the blade looked normal. I back tracked and found the missing part in the grass where I had just been. As it stands it vibrates so much i can not use it, and even if I tried it was really uncomfortable, and it would shake itself to death.

Here are some pictures. Is the chunk missing enough to cause a balance issue? I really like this mower and hope I did not kill it.

I have another blade, maybe I can try to swap the blade, perhaps it was damaged and I did not see it. Here are some pictures to help illustrate the issue. I repalced the blade, plug, and air filter in april, and the gas is reasonably fresh, and mixed properly.
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That chunk out of the deck wouldn't cause your vibration. I suspect that you hit something and then it hit the deck and took out that piece. I would inspect the blade and also possibly look for a wobble in the crankshaft when turned

I agree with the above post, sounds like you hit something substantial with the blade. Hopefully it just bent the blade, and not the crank. The good news is the Duraforce has the biggest diameter crank of all the Lawnboys ever produced so you stand a good chance that a new blade will get you back in service. I would however check the runout of the crank before purchasing that new blade. If the crank is bent I think I would just opt to replace the short block. Those short blocks are fairly cheap the last time I priced one.

Remove the spark plug and turn it over, and rotate the blade by hand, tie the hand lever down. Look for wobbles, and see if the tip of the blade meets the same point when rotated.

Re: Sudden onset of vibration [solved[

Thanks to all who replied.

I finally had a chance to look at this and the good news it that I did not see any crank wobbling, on my initial inspection I failed to notice the mulching fan lost a blade



I removed the fan, and everything was back to normal

I found 3 screws to hold the plastic shroud in place and I was able to finish mowing.

It looks like the short block is discontinued. I actually thought of buying one to hoard a few years ago but I seem to have missed my chance. I will order a new mulching fan before I need to mow again.