This article will touch on automotive fuels and how changes effect our vintage motorcycles.

Technical Report on Oxygenated (Ethanol Fuels) – Long read click here 

From Amal – Used with permission



Recent debates and publicity concerns surrounding the introduction and use of “Green Fuels”, has raised the question of the effects of these alcohol based fuels on the materials used in our components.

The use of ethyl alcohol mixed with petrol up to concentration of 10% (E10) has been common practice in the USA since the fuel crisis of the 1970’s. This blend is now regularly available in Australia and in limited supply throughout Europe. Higher levels of mixes, of 22% to 85% (E22 to E85) are used in Brazil and the latest trend has been for vehicle manufacturers to develop Flexible Fuel Vehicles (FFV’s).

These FFV’s and South American vehicles have all been specifically designed to accommodate the use of these high concentrations of ethanol.

Advantages and Disadvantages

The addition of ethanol to petrol has an effect on both the performance of an engine and also its interaction with the different materials it comes into contact with.

•    Change in Octane Number

The addition of ethanol, up to a certain level, improves the octane number ,giving better anti-knock properties that can be helpful to older and higher performance engines that were designed for high octane fuels.

•    Change in Volatility

A fuel’s ability to vaporize has an effect on performance and on emissions. The addition of ethanol has the effect of lowering the temperature at which the fuel vaporizes, thereby improving combustion and cold starting. However It can increase the possibility of a vapor lock.

    •    Increase in Oxygen Content

In addition to hydrogen and carbon , ethanol also contains oxygen. The replacement of hydrocarbons with oxygen has the effect of weakening the air-to-fuel ratio. This lowers emissions, lowers mpg and raises NOx in vehicles without a three way catalyst.

•    Effect of Water Solubility

The addition of ethanol causes fuel to become hydroscopic (absorbs water). This has several different effects. It becomes acidic and conductive causing both a chemical reaction with certain materials and galvanic reaction causing corrosion. As water is heavier than petrol, a layering effect can occur with stored fuel, having a higher water content settling to the bottom where fuel pick-ups are located.

•    Lubricating Effect

When mixing with 2 stroke fuels it has been noted this can cause phase separation in breaking down the oil and petrol content,causing a loss of lubrication. Under other conditions it can act as a solvent, washing oils from metal surfaces thereby increasing engine wear.

•    Permeability

Ethanol readily permeates through elastomers and plastics, resulting in a deterioration of these materials.

Component Design Compatibility

For fuel blends containing less than 5% ethanol, the concentration is low enough not to cause any significant effect. For 5% to 10% blend, some changes are recommended, (albeit that the USA has been subjected to this concentration for sometime without any known problems). For above 10% the effects of ethanol are known to cause problems and the necessary modification that would be required would extend beyond those of just our product content in a vehicle.


E0 to E10 blended fuels have been in use in the USA since the late 1970’s and have had no significant effect on the performance or durability of our product. Using blends above E10 are not recommended as effects of these have yet to be fully investigated.

The company is already effecting changes of materials in sensitive components. Needles will be produced in nickel silver whilst orifices will be made from manganese bronze. Diaphragms and O rings to be upgraded to Viton or other suitable material. Rubber petrol pipe to be internally lined or upgraded. This ongoing process should be completed by 2012.



What is one to do?

Use ethanol free fuel when available. Not always an option. We advise against trying to remove the ethanol from fuel as it is factored in as part of the octane rating. Removing the ethanol may lower the octane rating of the fuel and cause damage to the engine.

Upgrade float and float needles on all old machines. The white nylon floats (usually discolored yellow by fuel) should be updated to the Stay-Up black floats. These will not sink if the fuel dissolves a hole in the plastic. New viton rubber tipped float needles are a must.

Upgrade fuel lines to ethanol compatible hose. We offer several sizes.

  • Storage for several weeks

We advise that every time you put your bike away to shut the fuel taps and idle the bike till it quits. This will get the brass jets up out of the fuel. Preventing blocked and corroded jets.

  • Storage for months or years

Modern fuel will spoil a set of carbs and the inside of your fuel tank if stored long term. We advise draining your tank and float bowls into a fuel can before long term storage.

  • Putting a bike back on the road

Even with draining the fuel out of the carburetors you get some residual fuel in the pilot circuit. The pilot jet (a pressed in busing for many years) will get blocked and need cleaning. We offer a special jet tool for this. New production carbs in the Premier condition have a removal jet which is part of the brass block off plug.


Leave a Reply

Add a comment