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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14489
Experience:  Certified on Onan and Generac generators
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My Husky 5000 watt Generator with Subaru engine surges when

Resolved Question:

My Husky 5000 watt Generator with Subaru engine surges when on run and will only run smooth if on half choke. It is a new generator -- only used 3 times. The air filter is spotless, gas is always fresh and drained when in storage, Carb is drained when in storage as well. I always use Super Unleaded with fuel additives. When choke is set to run, if I cover the air intake about 2/3 with my hand, the engine runs smooth. Take my hand away and it surges. If I take the air filter completely out when running, the engine does not surge. I have put SeaFoam cleaner in the Fuel line and run several times. Surging does not improve significantly. Any ideas?
Submitted: 5 years ago.
Category: Small Engine
Expert:  Hank F. replied 5 years ago.

Hello!
Thank you for choosing Just Answer for the solution to your problem.
My name is XXXXX XXXXX I am going to assist you with this.

 

 

This is a classic symptom of a carburetor that has become plugged with varnish.

Yes, it can even happen on a brand new engine.

These engines are run at the factory to tune them, and they do not always get cleaned properly.

 

As gas gets old, it turns to varnish and clogs up the passageways inside the carburetor, not allowing enough gas to get to the engine.

This condition is cumulative. Every time gas sits, the varnish builds up just a little more, like coats of paint, until eventually gas can not flow. It will not happen overnight, but the symptoms can show up all of a sudden, even while simply stopping to refill with gas.

The use of fuel additives, such as Sta-Bil or Sea Foam will not stop this process from happening. They will greatly slow it down, but the gas will still go bad.

 

When this happens, either the engine simply will not start, or it will not run without the choke on (this reduces the amount of air getting pulled into the engine, changing the fuel/air mixture), or it will run but surges.

 

Another issue that varnish in the carb can cause is that the varnish may not allow the float needle to seal properly against the seat, causing the flow of gas to not shut off when the bowl is full. The result will be gas overflowing the carb and running into the cylinder, and possibly out the air intake. If the gas gets into the cylinder, it will seep past the rings and down into the crankcase. This will be evidenced by your oil level being over-full and/or the oil smelling like gas.

 

The only 2 solutions are to either replace the carburetor or give it a good, thorough cleaning.

When removing the carb, make sure to take a good picture, or make a good drawing of where all springs and linkages are attached. This will make reassembly much easier.

Most people believe that cleaning a carb involves removing the bowl and wiping it out, then spraying some carb cleaner through it.

This is simply insufficient.

To properly clean the carb, you must remove it, disassemble it (making sure to remove all non-metal parts), and soak it in a commercial solvent for several hours. Soaking it overnight is even better.

Then clean all solvent off with a spray type carb cleaner, making sure to get lots of cleaner into every hole and passage there is. Pay special attention to the tiny holes in the bore of the carb, under the throttle plate for the carbs that have these holes. Use lots of cleaner. And make sure to wear safety goggles to avoid getting the over spray into your eyes. There will be over spray.

Dry the carb with low pressure compressed air.

When reassembling the carb, make sure to use a carb kit, when one is available for your carb.

 

Occasionally, even a good cleaning is not going to be sufficient, and you may end up having to replace the carb anyhow. Be prepared for this.

 

If for some odd reason this does not help, please let me know so I can assist you further.

 

Customer: replied 5 years ago.
What is the benefit of a carb kit? Not sure what that is or how it would help
Expert:  Hank F. replied 5 years ago.

You probably won't need a carb kit.

You can most likely get away with a good cleaning.

 

A carb kit usually consists of a new needle and gaskets.

 

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