Craftsman LT1000 clunks after hitting rock

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  #1  
Old 04-29-15, 05:43 AM
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Craftsman LT1000 clunks after hitting rock

We have a Craftsman lawn mower LT1000 20HP model 917.271920. It had been running and cutting great.

The operator was riding the mower through a gate from the back yard to behind the fence when he ran into a big flat rock that was sometimes used to hold the gate open.

As he recalls, the blade was not engaged, and only the outside of the deck hit the rock. The blades look fine. However, the engine shut down immediately, and we have not been able to start it again.

When we turn the key, we just hear and feel a single loud thunk -- not just a click. With the transmission engaged (via rod in back), we feel the thunk under the hood and under the seat; when disengaged, only under the hood. The engine does not crank.

We tried to jump with a battery booster, but still only the single thunk.

The following sums up what we know:

Battery is new and has well over 12V
We also see 12V at the solenoid and at the starter
Cable connections look good
The fuse by the solenoid is good
We jumped the seat switch to make sure it was not the issue
The mower deck moves freely up and down
The mower freewheels, we can push it around

What would you suggest we check next? Thanks in advance!
 
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  #2  
Old 04-29-15, 06:16 AM
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Can you disconnect the spark plug(s) and turn the engine over manually ?
 
  #3  
Old 04-29-15, 07:29 AM
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The odd thing is the engine is well separated from everything and should be pretty well protected even if the blades hit something while running.

First I would examine the mower deck. Look at the front edge to make sure it's not bent back to where the blades could hit it. I'd also inspect the spindles and where they mount to the deck for damage. Next look at all the hanger and supports for the deck. Maybe something hit or moved the transmission. Make sure that the deck is disengaging so it's not engaged when trying to start the mower.

Once you've done a quick pass to rule out external, visible damage I would do as Vermont suggested. Remove the spark plugs, grab the pulley on the output shaft of the engine and try to manually turn the engine over. If you can turn it I would unhook the belts so you can just deal with getting the engine running as a separate issue from anything else on the tractor.
 
  #4  
Old 04-29-15, 10:08 AM
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Thanks for the suggestions. We'll try to turn the engine over with the plug removed. Will have to look at the manual to see where that pulley is located!
 
  #5  
Old 04-29-15, 12:32 PM
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The engine is a vertical shaft. It's crank/drive shaft goes straight up and down. The pulley will be directly under the engine and probably tucked up between the frame rails of the tractor. You can also remove the shroud from the top of the engine to get access to the cooling fan. A socket and wrench on the big nut in the center will allow you to turn the engine over or you can push on the cooling fan if you are careful. Just make sure to have the spark plug removed from the engine.
 
  #6  
Old 04-29-15, 10:48 PM
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Any chance the engine is low on oil?
 
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