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So I have a Crary Bear Cat Chipper/Shredder with a Briggs & Stratton 8 hp engine. It kickbacks when I pull the rope to start it and backfires. I replaced the ignition coil and flywheel so I don't think it's a timing issue. It has a new carburetor as well. My husband left it outside for the last 10 years and I am trying to resurrect it. All new fuel lines, fresh oil, new spark plug. It is getting a good spark. Rebuilt the fuel pump. The only thing I have not messed with is the valves or crankshaft. Anybody any ideas? Help!!!

To me sounds like a sheared flywheel key. Or the flywheel wasn't torqued to factory specs. Sounds like the ignition timing is off kicking back as it is.

Get the valves in spec. Probably never been touched. Wouldn't hurt to have good sealing valves that are in time. Inspect everything. Sitting outside for 10 years......

Dead compression release??? This is a beast L-head engine. Or you still have a fountain of water in the fuel system. Dump and clean out the tank as in new condition.

Welcome to the forum.

sounds like a timing issue. The spark is igniting the mixture so early that the piston goes the wrong way. I'd first ask why the flywheel and coil was replaced. And how one knows the correct flywheel is the one installed.

slomo said:

To me sounds like a sheared flywheel key. Or the flywheel wasn't torqued to factory specs. Sounds like the ignition timing is off kicking back as it is.

Get the valves in spec. Probably never been touched. Wouldn't hurt to have good sealing valves that are in time. Inspect everything. Sitting outside for 10 years......

Dead compression release??? This is a beast L-head engine. Or you still have a fountain of water in the fuel system. Dump and clean out the tank as in new condition.

Welcome to the forum.

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The flywheel key was not sheared and the flywheel was torqued to spec. I am leaning towards the valves. The gas tank was also given a good cleaning and new petcock and fuel lines. Yes, 10 years that is a long story for a different forum. lol I have also read about a bent crankshaft but he assured me he never abused the machine. I guess abandonment does not count.

sgkent said:

sounds like a timing issue. The spark is igniting the mixture so early that the piston goes the wrong way. I'd first ask why the flywheel and coil was replaced. And how one knows the correct flywheel is the one installed.

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The flywheel and coil was replaced because I had no spark. I had to take the flywheel off to inspect the key. Both were replacement OEM parts so I am pretty sure they are the correct ones. I have every manual on the engine including parts lists. I do have a nice spark now. Are you suggesting putting the old flywheel on to see if that makes a difference?

If you did not torque the flywheel to spec it may have sheared the key on the very first the engine fired. On these engines the they are torqued to 65 ft/lbs.

StarTech said:

If you did not torque the flywheel to spec it may have sheared the key on the very first the engine fired. On these engines the they are torqued to 65 ft/lbs.

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Key is perfectly fine and I torqued to 65 ft/lbs.

Install OEM flywheel. Possible you got the wrong replacement part on accident.

Or the valves are super loose causing high static compression causing the kickback.

Ignition magneto installed correct side up?

slomo said:

Install OEM flywheel. Possible you got the wrong replacement part on accident.

Or the valves are super loose causing high static compression causing the kickback.

Ignition magneto installed correct side up?

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Ok..went back to the old flywheel, torqued to spec and same result. The ignition magneto is install correct side up. I guess I should give it a valve job.

Think this is an L-head. If confirmed an L, take your TIME grinding the gap on the valve stems. Measure three times and recheck clearance. No going back.

Post engine numbers to be clear what you are working on.

Might be on to something here. Key looks good. Flywheel on right..... Or not. You can see the flywheel rotated on the crank just a touch.