Ariens with 20 hp B&S

S

ScaryLarry

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Jul 29, 2026
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Engine only rotates a little over 1/3 of a rotation and stops. Starter has been rebuilt and tested, new solenoid. The engine can be rotated by hand.
 
Model type and code so we know what you have. If it is a single cylinder, it is probably valves out of adjustment or broken compression release on the cam shaft.
 
First place I would start is the battery. Needs LOAD tested. Not some cheap new false negative Ohms reader like Autozone or Oreily's uses. Need a real deal carbon pile tester. Call around and find someone with a carbon pile tester.

 
ScaryLarry said:
Engine only rotates a little over 1/3 of a rotation and stops. Starter has been rebuilt and tested, new solenoid. The engine can be rotated by hand.
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If battery, starter, and all connections are good, most likely needs a valve adjustment.
 
X2 for check your valve clearance.
Possible failing starter or wire connection
What happens if you hook up jumper cables to the battery from your vehicle? Does it spin over correctly then?
 
hlw49 said:
Model type and code so we know what you have. If it is a single cylinder, it is probably valves out of adjustment or broken compression release on the cam shaft.
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It is a broken compression relief valve. I saw a video on YouTube. You back the compression off, you’ll hear an air sound, then cover the carb intake with a rag and turn over the engine. Once it starts rotating freely, pull the rag away, engine starts. Works every time
 
andrewslarge said:
What’s your plan now?
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Well, I have another mower with a 17.5 HP engine that I'm going to swap out with. The mower deck rusted out on the mower it is sitting on. Lucky to have it.If I get time, HaHa, I might rebuild the 20hp engine.
 
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