Small Engines (Lawn Mowers, etc.): Briggs & Stratton power loss, briggs and stratton, briggs stratton

Question
Hello John

Thanks for your help, it seems I have now found the problem, the auto throttle would not balance so it was opening and closing all the time the mower was running, I have bypassed the throttle and attached a cable so I can use manual control over the throttle, which works spot on.

At least the mower has had a service with the carb soaked and a new spark plug.

Not sure if it's any use to you but I have uploaded a few shots of the carb while it was off, it looks to be very basic with no way of changing the mixture that I can see anyway.

Pics are at  

http://smg.photobucket.com/albums/v476/Goatsmilkuk/Mower Carb/

Thanks again your help is much appreciated.

Stuart
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Followup To

Question -
During using the mower which is a Mccoulloch Electrolux 3846S, with a Briggs and Stratton Sprint 40 engine.

The engine revs began to increase and decrease and also blow out black smoke, the mower is just over 1 year old and only has light use.

The spark plug gets fouled with black and oil deposits even after being cleaned.

The problem occurred with no load applied to the blades.

The throttle is an auto one, that uses the fan blades to regulate it by what I can gather.

Is there anything I can do to repair the mower, such as clean out the carb, or is the engine on it's way out?

Thanks for any help

Stuart

Answer -
 Hello Stuart:

 The Black Smoke is an Indicator of the Carburator Flooding Slightly. The Carburator Float is Not Stopping the Flow of Gas Properly. Check the Gas Tank Cap. If the Cap isnt Venting the Tank, the Pressure in the Tank will Build and Cause the Same Problem. Remove the Gas Tank Cap and Run the Engine. If this Doesnt Clear up the Running of the Engine, then Clean and Overhaul the Carburator. Hope this Helps. Let me know what Happens, Please.

 Good Luck

 Respectfully

 John

Hello John

Thanks for the fast reply.

I have checked the cap and I can blow through it no problem and when taking the cap off, there was no release of pressure.Also runs the same with the cap off.

I have taken the carb off and cleaned it with a carb cleaner spray and blown through all the holes. I could not see a float anywhere just two pipes one shorter than the other that go from the base of the carb into the petrol tank.
The longer one has a fixed gauze filter, the shorter one has a gauze cover, underneath that looks like a small valve ? The only moving part I can find is the throttle in the carb.

The revs go right down to almost cutting out then go back up to full speed then drops again this happens around every 1 second, the smoke is ligthter in colour now, but the fouling on the spark plug is the same as before.

Thanks again

Stuart



Answer -
 Hello Stuart:

 Oops! I forgot to Ask you to Send me the Model, Type and Code Numbers Off of the Engine, Please. Does this Carburator have as Screw with a Spring Around the Threaded Area? If it Does, then Turn the Screw in Slowly and Lean out the Air/Fuel Mixture. Also Sometimes the Carburator May Require an Overnight Soaking to Clean it Properly. Hopes this Helps. Let me know what Happens, Please.

 Good Luck  

 Respectfully

 John

Answer
 Hello Stuart:

 Thanks for the Pics. You have the Non-Adjustable Carburator. Bad thing About these Carburators is If Cleaning them Doesnt Help, It has to be Replaced. The Auto Throttle wont Balance if the Carburator has any kind of Internal Problem. As you Stated you Soaked the Carburator and it had No Effect. This means the Carburator may have a Small Crack Inside the Carburator. If I Understand you Correctly you have Bypassed the Governor and Are Using the Throttle Cable to Control the Engine Speed. If this is True, Be Careful not to Over Rev the Engine. Thanks for the Input.

 Respectfully

 John