Troybilt Pony Briggs 17.5hp I/C OHV Engine Missing

[TiIngot]

This is on a 2006 Troybilt Pony, Briggs single cylinder engine. When mowing it intermittently developed a split-second hard misfire. It almost feels like it is a split second electrical short. Sometimes it is hard enough that the engine just about stalls, then picks up and runs. All I have done is put a piece of cardboard between the contact on the seat safety switch and cleaned the gas tank. It was getting worse, so we shut it off to use a backup mower. Then it would click or hum but not turn over to put it back in the garage.

The engine was frozen at the top of the compression stroke. The starter would not turn the engine, and I could not move the engine by hand from the top by applying pressure to the flywheel. Two weeks later the engine was still frozen, and I put a wrench on the belt pully and the engine easily freed up. I could again turn the engine over by hand. I pulled the plug and it was not wet with gas. I changed oil and found no visible shavings in the old oil. It started right up and ran with the misfire still there.

Where do I start to correct the misfire? Electrical/safety interlock short, fuel delivery issue, or spark plug coil?? Will valves out of adjustment cause an intermittent misfire and possibly the compression issue when the piston was stuck?

Lee

 

[Rivets]

First thing I would do is pull the dipstick and see if the oil level is above the full mark and smell it. If it smells like gas I suspect the the float needle is not shutting off gas in the float bowl, allowing gas to drain through the carb into the crankcase. Fix, remove the carb and replace the float needle and seat. You will then drain all oil and gas from the crankcase and replace with fresh oil. Most techs recommend changing the oil again after about a half hour of use.

 

[Auto Doc's]

This is on a 2006 Troybilt Pony, Briggs single cylinder engine. When mowing it intermittently developed a split-second hard misfire. It almost feels like it is a split second electrical short. Sometimes it is hard enough that the engine just about stalls, then picks up and runs. All I have done is put a piece of cardboard between the contact on the seat safety switch and cleaned the gas tank. It was getting worse, so we shut it off to use a backup mower. Then it would click or hum but not turn over to put it back in the garage.

The engine was frozen at the top of the compression stroke. The starter would not turn the engine, and I could not move the engine by hand from the top by applying pressure to the flywheel. Two weeks later the engine was still frozen, and I put a wrench on the belt pully and the engine easily freed up. I could again turn the engine over by hand. I pulled the plug and it was not wet with gas. I changed oil and found no visible shavings in the old oil. It started right up and ran with the misfire still there.

Where do I start to correct the misfire? Electrical/safety interlock short, fuel delivery issue, or spark plug coil?? Will valves out of adjustment cause an intermittent misfire and possibly the compression issue when the piston was stuck?

Lee

The valves need to be adjusted and verified that the compression release is functioning.

Your description is leaning towards a very worn camshaft and failed compression release mechanism on the camshaft.

 

[andrewslarge]

1. I thought you had a leaking carburetor and the cylinder was hydro locked. If you had pulled the spark plug when it was locked you would have had oil and gas coming out and the oil level would be very high.

2. This is a 20 year old mower and is it likely the key switch has a defect, possibly a wire chafing, or maybe a faulty safety switch?

3. The valves need to be checked as well as the cold compression .

Please let us know your findings?

 

[Auto Doc's]

This is on a 2006 Troybilt Pony, Briggs single cylinder engine. When mowing it intermittently developed a split-second hard misfire. It almost feels like it is a split second electrical short. Sometimes it is hard enough that the engine just about stalls, then picks up and runs. All I have done is put a piece of cardboard between the contact on the seat safety switch and cleaned the gas tank. It was getting worse, so we shut it off to use a backup mower. Then it would click or hum but not turn over to put it back in the garage.

The engine was frozen at the top of the compression stroke. The starter would not turn the engine, and I could not move the engine by hand from the top by applying pressure to the flywheel. Two weeks later the engine was still frozen, and I put a wrench on the belt pully and the engine easily freed up. I could again turn the engine over by hand. I pulled the plug and it was not wet with gas. I changed oil and found no visible shavings in the old oil. It started right up and ran with the misfire still there.

Where do I start to correct the misfire? Electrical/safety interlock short, fuel delivery issue, or spark plug coil?? Will valves out of adjustment cause an intermittent misfire and possibly the compression issue when the piston was stuck?

Lee

Have you been able to start and run it since the "lockup" incident and you were able to get the engine to turn again?