B & S 18 hp engine surging and popping.

[Bat57]

hey guys. I have a situation going on with 2 B&S engines. both are 18hp. Engine number on one is (31H7770297E1), Can't read the other engine number because of rust on valve cover but engine cover says the same thing as the first engine. They look like the same series of engine. The problem is that when I start engine, right off it starts surging and then like backfire. does this no matter the throttle position. The second engine just surges no matter the throttle. ok, here is what I have done to remedy with no luck. 1. new spark plugs. 2. Cleaned carbs then replaced with new carbs. Cleaned coil contacts and Flywheel Contact. Replaced Flywheel key. Sprayed carb cleaner around head gasket area while running but no change in engine performance. No oil leaks around head gasket area. Any ideas why this is happening would be of great help.

 

[Rivets]

Before digging deeper into the possible causes, I would check the valve clearances on all valves. It does sound like a fuel issue, but let’s look at the easy things first.

 

[Bat57]

Before digging deeper into the possible causes, I would check the valve clearances on all valves. It does sound like a fuel issue, but let’s look at the easy things first.

Thanks for answering. I forgot to list that I checked and set the valves.

 

[Tiger Small Engine]

Thanks for answering. I forgot to list that I checked and set the valves.

Clean OEM carburetors again correctly. If you don’t know how to, then take them to a shop. Always want to keep OEM carburetor unless it is too far gone. Also, need to check for air intake leaks.

 

[Bat57]

Clean OEM carburetors again correctly. If you don’t know how to, then take them to a shop. Always want to keep OEM carburetor unless it is too far gone. Also, need to check for air intake leaks.

Ok.Thanks

 

[slomo]

Typically surging is lack of fuel delivery as Tiger Small Engine was talking about or a dirty carb. Check there first as he recommended.

 

[Bat57]

Typically surging is lack of fuel delivery as Tiger Small Engine was talking about or a dirty carb. Check there first as he recommended.

Thanks. I have taken shroud off and cleaned engine and fins already.

 

[slomo]

I have taken shroud off and cleaned engine and fins already.

Yearly if not more often is recommended in our manuals. Good man......