Wrong Fuel in a Motorbike: What to Do Before You Start the Engine
Most wrong fuel advice out there is written for cars. But motorbikes get misfuelled too, and the situation is actually a bit different because of how a bike’s fuel system is built compared to a car’s. If you have just filled your motorbike with the wrong fuel and you have not started the engine yet, you are in the best possible position. Here is what to do and what to avoid.
How Does Wrong Fuel End Up in a Motorbike?
It happens more often than people think. The most common is grabbing the diesel nozzle instead of unleaded at a servo with combined bowsers. The diesel nozzle is bigger than a petrol nozzle, but most motorbike filler necks are wide open with no restrictor so the diesel nozzle just slides in.
It’s also the time when people fill up from a jerry can that previously had diesel in it, or when someone borrows a bike and fills it with whatever fuel their car takes. But a less dramatic version is when the rider accidentally puts E10 in an older bike that isn’t compatible with ethanol, or puts 91 in a bike that needs 95 or 98.
What Happens If You Put Diesel in a Petrol Motorbike?
Diesel does not ignite like petrol. Spark plugs are used in petrol engines. Diesel is much more difficult to ignite with a spark. If you put a large amount of diesel into a petrol motorbike the engine will have difficulty running, will misfire badly, produce heavy smoke from the exhaust and will eventually stall or refuse to start.
Diesel also deposits an oily film that can foul the spark plugs, clog the fuel lines and gum up the carburettor or fuel injectors. The longer the engine runs on it , the more it needs to be cleaned.
The good news is that diesel in a petrol motorbike is not as catastrophic as petrol in a diesel car. It won’t run right, but it probably won’t do the kind of internal damage petrol-in-diesel does to modern common rail systems.
What About E10 or the Wrong Octane Grade?
No issues at all if your bike is E10 compatible. If your bike is older or specifically states it should not have ethanol fuel, one tank of E10 will not cause immediate damage, but repeated use will degrade rubber fuel lines and carburettor seals over time.
If you put 91 in a bike that needs 95 or 98, you will lose some performance and the engine may knock under load. Next time fill up with 98 and drive nice until then.
What to Do If You Have Put the Wrong Fuel in Your Motorbike
The steps are the same as with a car, just on a smaller scale.
- Do not start the engine. If the fuel is sitting in the tank and has not been through the system, the fix is simple.
- Do not turn the ignition on. On fuel injected bikes, the fuel pump primes as soon as the ignition is switched on, pushing wrong fuel into the lines.
- Push the bike away from the bowser if you are at a servo.
- Call a mobile fuel drain service or arrange to have the tank drained.
On a motorbike the tank is smaller and more accessible than a car’s, so the drain process is usually quicker. In many cases the tank can be removed, emptied, flushed, and refitted.
Can You Drain a Motorbike Fuel Tank Yourself?
Technically, yes. Motorbike tanks are more accessible than car tanks and some riders with mechanical experience handle it themselves. But you need a safe way to store and dispose of the contaminated fuel, you need to flush the tank properly rather than just emptying it, and if the engine was started, the fuel lines and carburettor or injectors need attention too.
If you are not confident doing it yourself, a professional fuel drain is the safest option.
Frequently Asked Questions
Will wrong fuel damage my motorbike engine?
If you have not started the engine, damage is very unlikely. The wrong fuel is contained in the tank and can be drained out. If the engine was run, there may be fouled spark plugs and contaminated fuel lines that need professional cleaning.
Can a mobile fuel drain service work on motorbikes?
Yes. Mobile fuel drain services can drain and flush motorbike fuel tanks on site. The process is usually quicker than a car because the tank is smaller and more accessible.
How much does it cost to drain wrong fuel from a motorbike?
Cost varies depending on whether the engine was started and how much contamination has spread through the system. A straightforward tank drain on a motorbike is typically less expensive than a car due to the smaller tank and simpler fuel system.
What if I already started the engine on the wrong fuel?
Turn it off immediately. The sooner you stop the engine, the less contaminated fuel circulates through the system. It can still be drained and flushed, but additional work on spark plugs and fuel system components may be needed.
Need Help With Wrong Fuel in Your Motorbike?
If you have put the wrong fuel in your motorbike and you are not sure what to do next, call us before you start the engine.
Call Wrong Fuel Help on 0432 553 905. Available 24/7 across Newcastle, Hunter Valley, Central Coast, and regional NSW. We come to you.
