Should you drain a motorcycle carburetor? (You need to know)

Absolutely yes, if you are not starting the motorcycle for more than 1 month or storing it for a prolonged period. If you add a fuel stabilizer, this can be extended up to 3 or 4 months.

Although fuel injection has dominated the motorcycle world for almost two decades, there is still a large number of carbureted motorcycles still in use and will be the focus of this article.

Old fuel can cause havoc on almost all motorcycle systems, let alone a carburetor. A carburetor is the main component of a non-fuel injected motorcycle and controls the flow of fuel into the engine.

Here is the important part, the carburetor controls fuel to the engine whether the motorcycle is running or not, therefore, making sure it is drained when a motorcycle sits for a prolonged period without use is one of the most important things you can do.

Also, you should shut the fuel valve at the same time. Both of these together can greatly improve the life of a motorcycle and are highly recommended.

In this article, I will show you

Why you would you need to drain your carburetor?

A motorcycle carburetor supplies a specific air/fuel mixture that is used by the engine to create power. This is accomplished by having a small reservoir of gasoline available to draw from as air is sucked into the engine.

This means that a portion of gasoline remains inside the carburetor even after the engine is shut off!

Anytime gasoline is involved you should consider the shelf life. Yes over time, gasoline does lose its ability to burn either through deterioration or contamination thus, the term “goes bad”.

Wait, what, gas goes bad? You bet it does!

Why does gas goes bad?

There are 4 major things that cause gasoline to go bad oxidization, temperature, water, and container.

Oxidization is the chemical breaking of bonds of a substance to fuse with oxygen and it affects almost everything. It causes iron to rust, aluminum to turn black, and gasoline to go bad.

Temperature can really affect gasoline mostly due to evaporation and condensation. Rapid temperature variations should be avoided.

Water can get into the gasoline through moisture in the air. Seeing as water is a firefighter’s main tool, it’s probably not going to help your gasoline burn.

The container you store your fuel in can have a massive effect on gasoline and size matters! A small amount of fuel goes bad faster than a larger amount.

What happens when gas is left too long?

The problem is three-fold. Gasoline, as it destabilizes, can become corrosive and actually eat away at the components of your carburetor.

To see what this looks like check out carnage corner.

This can affect the way air and fuel move in the carburetor or worse cause a component failure. This can be a huge issue if you have a vintage or rare motorcycle.

The second issue comes when the gasoline starts to thicken. This is especially problematic in a carburetor due to all the tiny, virtually inaccessible passages that run throughout its construction.

In fact, I have seen gasoline thicken to the point sanding it off or even drilling through it can be a challenge!

The third can be just as problematic as the first 2 because as fuel destabilizes it also loses its ability to burn correctly causing a whole host of problems the worst of which can destroy the engine.

Will adding something to my gasoline help?

There are two common products added to gasoline, octane booster and fuel stabilizer.

Fuel stabilizer is a product that helps against the breakdown of gasoline’s chemical structure. One of the ways this is accomplished is an alcohol-based substance, typically ethanol.

Ethanol can help disperse water stopping it from dissolving in your gasoline. It is commonly used in products like lock deicer and varnish.

The other main ingredient is Hydro-treated Light Naphthenic Distillate Solvent Extract.

Hydro-treated Light Naphthenic Distillate Solvent Extract prevents changes in the chemical makeup of anything it is added to. This wonderful stuff is added to things like antifreeze and engine flushes.

Both of these together, plus a “Trade secret ingredient” is how fuel stabilizers help stop gasoline from deterioration.

Octane booster, on the other hand, is a substance that aids in stabilizing the burning of gasoline. It is comprised mostly of tetraethyl lead and alcohol (mostly ethanol).

Although this may help your gas burn to some degree but won’t help any stability issues.

The octane rating numbers which you may be used to seeing on the gas pump as 87 for regular and as high as 94 for premium refers to something a bit different.

Octane rating is a measure of a gasoline’s ability to handle compression without spontaneously igniting.

Now you know why and how gasoline goes bad, however, there is still some debate among experts.

The great debate

Clearly, over long periods of time, you need to drain your carburetor to avoid unrepairable damage. But how long does it take to reach the point of eating your carburetor parts or plugging its passages?

Well if you talk to the guys who work on lawnmowers, trimmers, and other power products they would tell you that plugged passageways and eroded parts are something they rarely see.

For them, it is the absence of gasoline that causes the majority of carburetor issues in smaller engines. Because they usually combine the fuel pump, primer, and carburetor all in one you now have a rubber diaphragm in the mix.

This can lead to issues because gasoline when it evaporates, has a tendency to dry the rubber used to make the diaphragm causing it to stiffen and worsen its ability to pump or worse yet crack or break.

Now how long it takes to erode your carburetor I can’t really say but what I do know is most of the time when I see structural damage the bike has been sitting in extreme conditions for more than 4 or 5 years.

Plugging passageways is another matter. I have seen under certain conditions, gas plug up passageways in as little as 1 or 2 months.

Typically under normal conditions, you’re looking at 3 to 4 months before your gasoline starts to thicken to the point it plugs things up.

Final thoughts

Gasoline is as harmful as it is useful. Learning how it works and how to keep it fresh is a great way to avoid many of the pitfalls of gasoline especially when it comes to motorcycle carburetors.

The best way to prevent gasoline from harming your motorcycle is to make sure it is not in your carburetor when not in use and keep the fuel shutoff valve closed.

Remember that the carburetor controls the flow of fuel to the engine whether it is running or not. If the components inside it fail you could end up with an engine filled with fuel!

Not to mention the fact that poor quality of gasoline can result in catastrophic failure to the point where broken components can be hurled through the engine case.

Hopefully, I haven’t scared you too much while explaining all this. Until next time keep enjoying things moto.