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.
Thanks for answering. I forgot to list that I checked and set the valves.
Tiger Small Engine
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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
Thanks. I have taken shroud off and cleaned engine and fins already.Typically surging is lack of fuel delivery as Tiger Small Engine was talking about or a dirty carb. Check there first as he recommended.
Yearly if not more often is recommended in our manuals. Good man......
As well as cleaning and adjusting the coils you might also unplug both the coil kill wires . There is a diode in each wire that allows current to go to the ignition switch to be shorted to the ground to stop the engine . If one of the diodes goes bad it will allow the pulse from one cylinder to go through the bad diode into the other cylinder coil and it will fire when it should not , the backfire could be unburnt fuel in the exhaust . If that has no effect on the problem try adding fuel to the carb with a unlit propane torch at the air cleaner, if adding more fuel stops the surge then you are back to carb work. Check the gasket between the carb and the block or plastic insulator make sure it is in the right way for holes to line up with each other .
I am close to a auction house that sells store returns so I saw a lot of Champion generators , they are brand new out of box that ran every way but right. I worked on the first one for 8 hours, I had the carb off so many times I wrecked the gasket between the carb and engine . So I made one using the carb as the pattern and it ran fine. I had already ordered a new carb and the gasket that came with it did not match the one I made , but I tried it and it ran like crap. It blocked a little hole that allowed air in. It is all ways the last place you look.
I am close to a auction house that sells store returns so I saw a lot of Champion generators , they are brand new out of box that ran every way but right. I worked on the first one for 8 hours, I had the carb off so many times I wrecked the gasket between the carb and engine . So I made one using the carb as the pattern and it ran fine. I had already ordered a new carb and the gasket that came with it did not match the one I made , but I tried it and it ran like crap. It blocked a little hole that allowed air in. It is all ways the last place you look.