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I think my is gummed up on my Deere D170. Sat over the

I think my carburetor...

I think my carburetor is gummed up on my John Deere D170. Sat over the winter. Fresh gas and flushed before starting. Starts fine but after running fir a bit I have to choke the engine to get it back up to speed. Problem repeats. Dies the die so long as I periodically choke it

Mechanic's Assistant: Do you have fuel in the tank? If so, is the shut-off valve open and the fuel clean?

New fuel but might be a couple of months old. Starts fine on choke

Mechanic's Assistant: Do you plan on doing the work yourself?

Does it sound like a gummed up carb?

Mechanic's Assistant: Anything else we should know to help you best?

That's everything

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Answered in 7 minutes by:
3/19/2018
Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15,636
Experience: Certified on Onan and Generac generators
Verified

Hello, my name is ***** ***** I am going to assist you with this.

Yes, that definitely sounds like a gummed up carburetor.

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.
Today’s gasoline formulation goes bad in as little as 30 days.
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.

This can also happen even on a brand new engine or brand new carb. When the carb is built, it is run at the factory to tune it.
After tuning, they do not always get properly cleaned, or may not have enough/any preservative injected. Believe it or not, this is actually fairly common.

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.
If this is the case, you will need to change the oil and filter, if it has a filter.
Varnish can also cause the float needle to stick shut, and not allow any gas to flow from the carb bowl into the engine.

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. It takes months or years for this accumulation to build up – it just can not be removed in minutes.

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.

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Customer reply replied 1 month ago
Thank you Hank. I'm a decent weekend mechanic but certainly no expert. Would you suggest I try to to remove and clean the carb (I'm assuming that there is a specific carb rebuild kit), or take it to a small engine specialist? Never done a carb on a small engine and haven't done a car carb since the seventies...

If you've cleaned a car carb, this will be a breeze.

If this carb has adjustable jets, make sure to note the position of them before removing them.

There really isn't much to these carbs.

Definitely get a kit if one is available for your engine.

Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15,636
Experience: Certified on Onan and Generac generators
Verified
Hank F. and 87 other Small Engine Specialists are ready to help you
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Customer reply replied 1 month ago
Thanks Hank. I've got a couple of other small engine projects so you'll probably hear from me again. I need to finish this first while I can still find the yard

I hear you. If this rain doesn't quit, I won't have a yard this year.

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Hank F.
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Category: Small Engine
Satisfied Customers: 15,636
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Experience: Certified on Onan and Generac generators

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