Is gasoline spoiling or deteriorating the main cause of carburetor problems?

This is the article translated from NOUKINAVI blog.
You can find the original post (in Japanese) here: キャブレターの不具合は、ガソリンが腐る・劣化するが主な原因? | ブログ|ノウキナビ (

In this article, I’d like to talk about carburetors, which are always attached to gasoline engines, not just agricultural equipment.

In the first place, what are some of the problems with carburetors?

  • Idling is not stable. (breathing)
  • The RPM does not drop when the gas pedal is turned back on.
  • Fuel overflows. Fuel overflows (leaks)

In most cases, these symptoms do not appear suddenly, but gradually progress. Therefore, if you leave even a slight problem untreated, you may not be able to start the engine. So, why do carburetors fail in the first place? The main reason is that gasoline rots and deteriorates.


Causes of gasoline spoilage and deterioration

The cause of gasoline going rancid is deterioration in quality due to long-term storage or contamination with impurities. It is important to note that even small things such as the fuel oil cap not being closed properly can accelerate the deterioration.

In addition, when the substance called “alkene” contained in gasoline comes in contact with oxygen in the air, it is oxidized to formic acid or acetic acid, and volatile components are released. I’ve never heard of this before.

When gasoline goes bad, it produces a pungent odor and a sludge-like substance.

Deteriorated gasoline is easily recognizable because it has a distinctive smell. It oxidizes and turns into a pungent odor.

Also, gasoline left in the tank will corrode, leading to corrosion of the tank and engine. This is because acid has the property of dissolving metals.

In addition, when the volatile components are removed, a sticky, sludge-like substance is produced, which can cause contamination and clogging, resulting in problems such as the engine not running.


How long is the expiration date of gasoline? How long does it take to deteriorate?

It is said to be about six months in a cool place with little temperature change. When it is exposed to air, it can deteriorate in about three months.

Since the gasoline in the fuel tank is not exposed to air, it is said that it can be used for about six months, but it would be better to use it up soon.

What did you think?

In any case, I think it is best to drain the gasoline from the carburetor of agricultural equipment that will not be used for a long time (during the winter) and store it.

This alone will make a big difference, so please give it a try.

In addition, we recommend that you have your farm machinery inspected and serviced to ensure that you can use it more comfortably.

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