Engine blowing white smoke

[Jssussex]

I turned off my lawn tractor and my 12.5 hp single cylinder b&s started blowing a huge amount of white smoke, ran for 10 seconds and stopped. It appears the tractor is passing fuel trough to the exhaust system. Any suggested diagnosis would be appreciated. Is the engine shot or is it worth tearing down and rebuilding. It's probably has 300 hours on the engine.

Any suggestions would be appreciated.

 

[oldnslo]

I would check the fuel inlet needle and seat assembly in the carb. These are a wear item and when the needle and seat start to leak they will flood the engine.

 

[Jssussex]

I would check the fuel inlet needle and seat assembly in the carb. These are a wear item and when the needle and seat start to leak they will flood the engine.

Would you just close the needle valve to see if that resolved the problem? What threw me was I had used the tractor 3 or 4 times and this was a sudden failure. I restarted it to day and in about 30 seconds it was doing it again.

 

[oldnslo]

By needle valve are talking about an in-line fuel shut-off valve? If you have this valve you can try closing it and run the engine until it starts to run out of fuel and then reopen the valve. You might have just trapped a small piece of dirt in the carb needle and seat and this might flush it out.

Otherwise the needle and seat i was talking about require the carb be dismantled. Usually all you have to remove is the float bowl to access the needle and seat. If you have the model and type or code numbers you can go to Lawn Mower Parts & Small Engine Parts by Briggs & Stratton and they have IPL's (Illustrated Parts List)on-line

 

[Jssussex]

I would check the fuel inlet needle and seat assembly in the carb. These are a wear item and when the needle and seat start to leak they will flood the engine.

You were correct and the simple solution was to add a shutoff to the gas line and turn off the gas line when the tractor isn't running.