20 Hp Briggs 460777-2277-E1 Low Power

[renegade2k]

I have the above Opposed twin engine in a Murray lawn tractor and it runs great until I go up a hill with the blades on, or I mow above half speed.

I would expect that an engine this size would handle mowing at full speed(with the obvious bad Cut), but would not drag the engine slow.

I have tried pulling the choke, but it only makes it worse.

I am used to adjustments on tractor carbs, but the jets are not adjustable.
I am unfamiliar with this engine and don't know if the fuel pump on the carb could cause this problem.

I did notice that fuel comes out of a brass tube in the carb (on the wall with the fuel pump) when the engine is running with the air filter off. The fuel is usually sucked into the carb. I don't know if this is normal or not.

 

[Scooby074]

How exactly is it behaving? a little more detail would help.

Have you done anything to it lately? Cleaned the carbs? Plugs?

First thing id do is pull off each plug at a time wire with the engine running and see what happens. If it dies with one disconnected the engine is running on one cyl. The coils in those engines are known for problems.

Another problem is the key on the flywheel. but thats more in depth.

 

[Craig Clayton]

Another thought depending upon the hours is your inline fuel filter clean?. Check under the cooling fins for a mouse nest that will heat up an engine, also when going uphill are you low on fuel ,topup the tank. Do you have the proper engine oil in maybe straight SAE 30 would help.
Craig Clayton

 

[BriggsStratton]

If you are still in need of repair for your engine I would recommend that you try what Scooby074 said to try. The issue that you are having seems to be that the engine is only running off of one cylinder. The test he mentioned will be determine whether the engine is firing on both cylinders or not.

If the engine is firing on both cylinders the issue that you are having may lie with the carburetor. A partially blocked jet or port in the carburetor can cause the engine to starve for fuel as well as not allow the fuel to properly mix and ignite.

 

[Treemonkey1000]

Cleaned your air filter lately? That is take it out and clean it or remove it and try the hill again. DO not run long without the airfilter. Clogged fuel filter will get you as well. Have you put any fresh gas in the tank? If you had an old can of gas around and dumped that in there it may be skunk gas which won't run well in your machine.

 

[mostly_gas]

If pulling the choke on makes it worse then it is likely running too rich. Spark plugs being black will confirm this condition. Air filter clogged or float valve dirty are two most likely culprits.
If plugs not black try replacing them. Worn misgapped plugs can cause problems.