Can I Run AvGas In My Dirt Bike?

AvGas, also known as Aviation Gasoline, is appealing to riders because of the high octane rating, low price (when compared to race gas), and its relative availability. These benefits make it out to be an obvious choice when looking for high octane performance, but some aspects would suggest otherwise.

What Is Octane - FeaturedWhat is AvGas?

AvGas LL 100, which is the shortened form of “Low Lead 100 Octane”, is leaded gasoline mixed with Tetra-ethyl-lead (TEL) at a high volume of lead at 1.9 milliliters per US Gallon. As a result, it tends to leave a large number of lead deposits in the vehicle’s motor. While TEL is the traditional way to increase octane, AvGas still differs significantly from motor vehicle race gas.

AvGas is a blend that has been designed for long-stroke, large-bore engines that have steady, low RPM, and run at high altitude. Even though this can be useful in any engine, the preferred option for shorter-stroke, smaller-bore engines that have high RPM is to use quality octane boosters or racing fuel. The whole point of using AvGas is its low volatility. But you will compromise cold starts, idling, and part-throttle performance if you use it in ratios higher than about 40 percent.

Related: How Are Octane Ratings Tested?

Problems With High Octane Short Cuts

Post-combustion lead is corrosive to the cylinder heads, valve guides, valve seats, and valves themselves. These deposits will block the oxygen sensors and catalytic converters, as well as damage the spark plugs, and it doesn’t take long. 100LL uses a chemical combination that makes it perform at high altitude, which doesn’t help when the motor is on the ground.

AvGas has a lower specific gravity. Lower gravity means that you must change the air-fuel ratio calibration to get the engine to perform optimally. LL100 has a large percentage of aromatics as well, which causes a reduced throttle response, which is an issue with high-performance motorcycle engines. The aromatics can also damage the rubber components like injector washers, fuel pump seals, and fuel lines in motorcycle fuel systems.

Related: Don’t Run Ethanol In Your Dirt Bike!

Where To Buy AvGas

AvGas sales are heavily regulated, as well as its use. Many fuel dealers for aircraft will only sell AvGas if they fuel the aircraft themselves. A legal grey area exists, as small gas stations next to private airstrips sell AvGas from standard fuel pumps. So once it’s in the tank, it’s not their problem.

Working with such a loophole is how some people get AvGas to use in other types of vehicles. Since AvGas does not have any duties or taxes on it, you cannot use it on public roads.

AvGas is suitable for certain engines, namely ones that do not contain oxygen sensors or catalytic converters. It also is alright to use in dirt bikes that are rebuilt frequently, because the build-up of lead is not a problem. Be sure to use a race fuel that is unleaded or a high-quality octane booster for any other applications.

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