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Discussion Starter #1 (Edited)
So Im not an engine guy but trying to figure out the issue with my LA115 riding mower. Need to try and fix myself.

I ran over a heavy chain which made the engine and blades come to an instant stop. After removing chain the mower started right back up and ran fine for a week then all the sudden the starter would not spin up the flywheel. Kept hanging up. So I got a used starter and replaced the battery but still have the issue. A friend said it might be the flywheel key so I took off the flywheel and the key was intact. He also suggested removing the plug to see if the motor would spin up and it does just fine. It seems once there is compression/resistance the starter will not spin up the flywheel. It will eventually start after it catches a free spot maybe after about 15 tries. So not sure what to check next. Maybe the crankshaft is damaged, or the pistons, rods, I dont know Im not a small engine guy just trying to fix it. When I do get it started it runs fine.

Its a JD Mower but the engine is a Briggs and Stratton 19.5hp OVC

Thanks in advance for any help
 

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The two most common reasons for this, besides battery and starter, are the valves are out of adjustment or the camshaft has a broken compression release. If you have a compression tester perform a compression test. Should not be over 100 PSI. If over, adjust valves and do compression test again. If it went down, good. If it didnt, you will need a new camshaft and tappets.

Valve adjustment as follows..Sorry the pics wont copy/paste

2. Remove four bolts and valve cover (A).

3. Disconnect spark plug wire (B) and remove spark plug (C).

4. Place thumb or finger over spark plug hole and turn crankshaft (clockwise viewed from top, counter clockwise viewed from bottom) until air pressure is felt in spark plug hole (engine is on compression stroke).

5. Insert a screwdriver through the spark plug opening (D). Slowly continue to turn the crankshaft until the piston has pushed the screwdriver to the top of it's stroke and has started to move down again approximately 6.35 mm (0.25 in.).

6. Check valve clearance with a feeler gauge (E) between valve stem and rocker arm. Valve clearance should be 0.08 - 0.13 mm (0.003 - 0.005 in.) for the intake (bottom) valve, and 0.13 - 0.18 mm (0.005 - 0.007 in.) for the exhaust (top) valve.

7. If not within specification, adjust as necessary by loosening set screw (F) and adjusting nut (G) until slight drag is felt on feeler gauge. Hold nut with wrench and tighten set screw to 7 Nm (60 lb-in.).

8. Recheck clearance and make adjustments if necessary.

9. Install spark plug. Tighten to specification.

10. Install valve cover with new gasket. Tighten screws to specification.

Specifications:
Lock Nut 7 Nm (60 lb - in.)

Valve Clearance
Intake 0.08 - 0.13 mm (0.003 - 0.005 in.)

Exhaust 0.13 - 0.18 mm (0.005 - 0.007 in.)

Valve Cover Cap Screws 7 Nm (60 lb - in.)

Spark Plug Torque 20 Nm (180 lb - in.)
 

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Discussion Starter #3
Wow, that sounds like a challenge. Where did you get that info ? would like to view the pics, thats would be helpful.
 
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