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Which gas to use for your new bike - Fuel system components

Which gas to use for your new bike - Fuel system components

It’s all about the gas!

Welcome to this week’s tech talk at Venom Motorsports!

Customers have been asking me...Tim, which type of gasoline should I run in my bike?

Today we are going to spend some time discussing the fuel system found in your bike and which fuels are better for both performance and longevity of your bikes engine.

Please click on our “Fuel System Component” video link below to view the fuel system components and their location on our Venom 125 cc ATV.

Keep in mind that this information applies to all of our excellent gas powered Super Pocket Bikes, Dirt Bikes and ATVs!

Ok onto this week’s topic.

Tim...Is one Gasoline better than another?

To begin with you need to understand the KABOOM equation.

Spark + Fuel + Air = KABOOM!

When KABOOM occurs the piston is pushed downward in the engine cylinder, which turns the crankshaft, which turns the gears in the transmission, which drives the chain, which turns the rear wheel gear, which makes you go zoom! So KABOOM is most important!

Today we are looking at the Fuel side of the KABOOM equation.

Better gas does = Better KABOOM

So what is better gas? Gas is a blend of different fuels.

Typically the blends are very similar and all have very similar energy values.

The difference in gasoline "quality" so to speak is more a function of its “freshness” and if it has detergent agents in it or a small amount of ethanol.

Tim...Is the Octane level of the gasoline I use important for my bike?

Octane is a gasoline rating system that indicates how much the air/fuel mixture can be compressed in an internal combustion engine before it spontaneously ignites. Octane is an additive to gasoline to resist premature ignition. It does not affect the energy value of the fuel.

You may have heard of the term “engine knock” or “ping” these are terms used to describe the noise produced when your engine is suffering from early detonation.

In a typical gas powered engine the air/fuel mixture enters into the engine cylinder on the intake stroke and is then compressed during the compression stroke. As the name implies the air/fuel mixture is compressed as the piston moves from bottom dead center to top dead center. The greater the volume of air/fuel mixture compressed, the higher the compression ratio of the engine. High Octane levels are really only needed on those engines with a compression ratio higher than 10:1. This means for example that an engine with a compression ratio of 10:1 will compress an air/fuel mixture of 10 cubic centimeters to 1 cubic centimeter in volume.

It is during this compression that the air/fuel mixture heats up due to the heat of compression and residual heat in the engine cylinder walls. If there is too much heat, the air fuel mixture will pre ignite before the spark plug fires and this can cause an unbalanced pressure wave in the cylinder producing unbalanced force on top of the piston. Typically we want the air fuel mixture to ignite just before the piston reaches top dead center of the compression stroke. This is done with the spark plug located right in the middle of the cylinder head and perfect engine timing. This ensures that the fuel ignites evenly and produces a pressure wave evenly across the piston head. However, sometimes while the main fuel ignition is occurring a separate spontaneous pocket of ignition will occur closer to the sides of the cylinder wall.

When the piston is acted on by unbalanced or uneven forces pushing it downward it will be pushed to one side, this is what does the damage to the piston rings, cylinder wall, cylinder head and makes that funny “ping” sound. If your engine ever makes a funny “ping” sound jump up to Octane level 91 right away. Again I have never heard the funny “ping” sound coming from one of our bikes. Typically our bikes have compression ratio’s in the 8:1 range and work just fine with an Octane level of 85 or 87.

If you drive a Ducati or Harley Davidson bike then you will need high Octane fuel 91 or 94.

When choosing a gas station, try to pick one that refills their fuel tanks often. You are looking for the busy gas station...not the one with three customers a day.

This will ensure that you are getting “fresh” gas and I also prefer gasoline’s that have detergents in them to help keep the fuel system clean.

Detergents in fuel oils and a excellent 10w40 motorcycle oil will help to keep your bike running in peak form for a long time.

Tim...What are the components typically found in the fuel system on my bike?

Fuel tank, petcock, fuel filter, fuel lines and carburetor.

The fuel starts off in the fuel tank than flows from the fuel tank through a petcock which acts as an on/off valve, than through the fuel filter to finally reach the carburetor.

On your bike all of the fuel lines are attached by simply pushing them onto ribbed fittings. This is known as a friction fit and is just fine as the fuel system is not under a high pressure. The fuel lines are made of a very flexible plastic materials and need to be checked to ensure they are not kinked over and restricting flow.

Any obstruction to the flow of fuel to the carburetor will lead to a loss in performance or a “no start” condition.

You would not believe how many people call me with a “No Start” bike condition, only to find out that they did not open the fuel “petcock”.

Tim...How often should I change the fuel filter on my bike?

The basic rule of thumb I use is everything three years. This works well for bikes driven on the street.

If we are talking about a dirt bike or ATV then to be safe I would change the filter every two years or sooner depending on the condition of the filter. These days most fuel filters come with a clear outer casing, so you can actually see the filter. When the filter media looks dirty, replace it. It’s that simple.

Inside your carburetor you will have too very small ports that the fuel must flow through to mix with combustion air and enter the engine cylinder on the intake stroke.

One is an idle port or jet and the second is the main jet. These have holes which are about the size of a needle or smaller. Needless to say any containment in the fuel will plug these up.

So where does all this dirt in the fuel filter come from?

Some of the dirt came from the gasoline vender and the rest from the environment in which you are driving your bike.

All fuel tanks have air vents...so air is always going to be coming in contact with your gasoline in the tank. The question is...how clean is that air? Any contaminants in the air will find their way to the fuel, then the fuel filter.

Once the flow rate of fuel is reduced to your engine, the engine will perform poorly or “bog” down.

Changing the fuel filter is an easy process as you need only remove and re-attach the fuel inlet and outlet lines.

Tim...What does Carburetor cleaner do?

Overtime, carburetors and choke assemblies can become clogged with gum, varnish and dirt, affecting performance. Carburetor cleaner quickly removes these deposits from the inside and outside of the carburetor to improve engine performance and fuel economy.

There are many carburetor cleaners in the market place. Most work pretty well and you need only spray them into the carburetor throat to clean the carburetor.

Better living through chemistry! Gotta love it!

Tim...What should I do to prepare the fuel system for winter storage.

Gasoline that sits for extended periods of time loses some of the volatile compounds by natural evaporation. So old gas will not ignite or perform as well as “new” gas fresh from the service station.

I always recommend that you drain the fuel tank and run the bike engine to burn off all remaining fuel in the carburetor fuel bowl. Once the bike stalls out then there is no more fuel in the carburetor at all.

This is a good practise before putting your bike away for winter storage in your garage where temperatures could drop as low as -40 F depending where you live.

This will ensure that there will be no gummed up components inside the carburetor due to waxes falling out of solution as the fuel is chilled to low temperatures during the winter months.

If you plan on storing your bike in your living room to polish it up during the long winter months, then it is fine to leave the gas in the bike.

I would also add some fuel stabilizer to keep the gasoline in top shape for that first start up in the spring.

Thanks for reading my blog this week and please subscribe to my tech videos on “youtube”.

To watch our video on Fuel Systems click here

Next week we will take a look at the Combustion Air System on your bike and as well discuss the importance of using good engine oil.

If you have any tech questions about our bikes, please feel free to email them to...


Enjoy the ride!


Technical Support Specialist

Venom Motorsports Canada



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