Briggs Intek, replaced everything, still surging.. Ideas?

[loopback1957]

Own a JD La115 with an Briggs Intek 19.5 engine. Have an issue with surging and backfiring when not under load. Have replaced fuel filter, gaskets, carburetor, spark plug, fuel pump, ignition coil/spark plug wire, air filter, adjusted valves, pumped out and refilled gas tank. Still have a surge/race condition and random backfire happening at any throttle position while at rest and during movement, it does smooth out when I engage the mower blades. I noted another post about surginng which indicated that the safety switch could somehow be involved, not sure I understand hwo that could be. Completely out of ideas and open to suggestions.

 

[StarTech]

Sounds the high speed idle circuit is too lean. Applying a little choke should clean it up and it does then it is a lean burn issue.

 

[Auto Doc's]

Own a JD La115 with an Briggs Intek 19.5 engine. Have an issue with surging and backfiring when not under load. Have replaced fuel filter, gaskets, carburetor, spark plug, fuel pump, ignition coil/spark plug wire, air filter, adjusted valves, pumped out and refilled gas tank. Still have a surge/race condition and random backfire happening at any throttle position while at rest and during movement, it does smooth out when I engage the mower blades. I noted another post about surginng which indicated that the safety switch could somehow be involved, not sure I understand hwo that could be. Completely out of ideas and open to suggestions.

A safety switch would not produce this kind of problem.

Please provide the number information stamped in the top of the valve cover on the engine.

Lack of proper choke operation is my initial thought with this running problem.

Next idea is the carburetor to cylinder block seal is leaking.

 

[loopback1957]

A safety switch would not produce this kind of problem.

Please provide the number information stamped in the top of the valve cover on the engine.

Lack of proper choke operation is my initial thought with this running problem.

Next idea is the carburetor to cylinder block seal is leaking.

Model 31P677 Type 0132 B1 Code 080213ZD

 

[loopback1957]

Model 31P677 Type 0132 B1 Code 080213ZD

Checked choke operation and linkage, choke appears to be opening and closing as it should. Will check carburetor to cylinder block and reseal with new gasket tonight.

 

[loopback1957]

Sounds the high speed idle circuit is too lean. Applying a little choke should clean it up and it does then it is a lean burn issue.

 

[loopback1957]

Sounds the high speed idle circuit is too lean. Applying a little choke should clean it up and it does then it is a lean burn issue.

Will check tonight

 

[slomo]

All those OEM Briggs parts? If not, every one will require testing. Could have a Chinese carb. Counterfeit plug. Over torqued gasket sealing area. Set valves wrong, IN and should of been EX.

pumped out and refilled gas tank.

Tank needs to be inspected for full flow into a glass jar or fuel can. Any elbows will catch trash and clog the flow from the tank.

No load it hunts. Under load with blades on, it smooths out. Would of thought the other way around.

Where is it backfiring from exactly? Carb or muffler? Could be a slipped flywheel key.

 

[slomo]

What RPM is this happening at? Are you running her at low revs? If you are under 3400 revs, not recommended due to lack of air cooling and lubrication.

 

[Oddjob]

I was recently gifted a Craftsman YS4500 with a 20HP Briggs single cylinder. It had been sitting in a neighbor’s garage for at least 5 years, probably longer, because “it was blowing smoke out of the muffler.” It turned out to be a blown head gasket. Looking at the consumer comments of those who bought head gaskets for Intek engines, I learned that these big Briggs Inteks go through head gaskets like the Gabor sisters went through husbands. In my research I also read that a bad head gasket could cause surging. I notice that you have replaced everything else. So, maybe do a leak down test and eliminate the head gasket as the cause. Or, just replace it. Intek head gaskets are really cheap and easy to replace and if your engine is typical, you’ll need to replace it in a year or two anyway. Good luck.