Briggs 331777-0956-B1 Runs and then it doesn't!?

[dart451]

Ok, got this Craftsman tractor, 917.288210 with Briggs 331777-0956-B1 engine. Customer told me it was running rough and then he could no longer get it started. To make a long story short, I removed carburetor, took apart and did notice some water in the carburetor. I said, ah ha! Well, cleaned it all up, the small o-ring was bad in the Nikki carb so I replaced with 698781 Gasket-Float bowl kit. Drained fuel from tank, filled with fresh gasoline. Noticed engine oil looked like chocolate milk...drained oil, changed oil filter and renewed with fresh oil. So, all back together, started fine...ran for awhile and engine starts doing exactly the same thing after about 20 minutes of running. Starts running rough, I can choke it to keep running and after a little bit, it straightens out again and is running fine off choke. This happened about 4-5 times however. Everything SHOULD be fresh, no water, fresh gas, completely cleaned carburetor. So...anyone have a clue what might be happening with this Nikki carburetor? I have grown to hate them with a passion!

[bgsengine]

Do a leakdown test, check for blown head gasket?

[KE4AVB]

Nikki carburetors are not that bad though it does take some learning them.

A couple thoughts from a couple that drove me about crazy doing about the same thing. It does sounds like water or trash is still in the system.

Does this mower have a regular fuel filter and not one of those pancakes? If so it might still be injecting water into the system if it has not been changed.

Also if you can shut the engine down immediately when it starts and check the fuel bowl for water.A simple catch pan and the removal of the anti fire solenoid should be enough to tell if water or trash is present. If trash then change out the fuel line.

I did have one that a kid gave his father dose of dirt and the changing of the fuel was the only way to clean it permanently.

[dart451]

The fuel filter was changed by the owner prior to me getting the mower...its one of those pancake type. Like I said, I did drain the tank as much as I could...

[KE4AVB]

The fuel filter was changed by the owner prior to me getting the mower...its one of those pancake type. Like I said, I did drain the tank as much as I could...

It doesn't take much water to cause problems actually less than teaspoon. You must completely drain the system IE the tank must be bone dry before adding fuel. Even more important if you use E10 or greater fuel as the water will settle out some the ethanol too adding to the problem. My Bolens mower had this problem as just small amount was present in the tank it would do exactly what you are describing.

BTW Using water is one way you can test for ethanol present in fuel as it causes the ethanol to separate from the gasoline.

Now the oil color. You said like chocolate milk. Was look like coffee with creamer in it or just burnt oil?

[dart451]

No, it was like cream in coffee...and I believe it was also water that got into the crankcase probably via the fuel system. The little O-ring inside the Nikki carb was in bad shape...must have been leaching into the cylinder for awhile. I thought that perhaps I'd smell some gasoline in the oil but I poured a little out on the gravel and it would not take a flame!

Just for more information...I've run the tractor a lot more here lately...seems to have no more problems...gonna check it again tomorrow though...