While many modern bikes incorporate many of the same bells and whistles as cars, a bike engine is still a pretty straightforward operation.
Once it starts, a combustion-based motorcycle engine requires air, fuel, and ignition to stay in motion.
This article explores the most common reasons why a motorcycle shuts off while riding but then starts back up. Not only that, it offers you troubleshooting tips and solutions along the way.
1. Fuel System Failures Trigger Limp Mode
On modern motorcycle engines, critical functions are controlled by intricate engine management systems all governed by the ECU (Electronic Computer Unit).
If your bike’s ECU detects even the tiniest abnormality in your fuel system’s operation, it will enter your engine into a “limp mode.”
A motorcycle’s limp mode restricts the engine’s power to lessen the long-term risk a severe fuel system failure poses to your engine.
- Some of the more modern motorcycles with infotainment and monitoring systems have a method of warning the rider when the engine enters limp mode and why.
- More straightforward motorcycle models need to be hooked up to a computer diagnostics unit to determine the cause of the ECU’s alarm.
- In other cases, a faulty fuel system sensor relays a problem to your ECU that doesn’t exist due to a defective connection, throwing your bike into a limp mode for no real reason.
Regardless, if your bike’s Electronic Computer Unit detects an issue with the fuel system and enters limp mode, your bike will lose power and shut off during acceleration. To learn more about this, read about why a motorcycle shuts off while riding here.
Shutting off your power should clear the codes that tripped the ECU, and it should allow the bike to start back up. If your sensor misread something, your motorcycle would run fine. If the bike enters limp mode again, there’s either a failure elsewhere in the engine or with the sensor/ECU.
Sensors fail due to corrupted wiring and corrosion. This is why ECUs need to be flashed and updated often by motorcycle technicians. If there’s an issue with your fuel system causing your bike to enter limp mode, the techs can pull the codes from the ECU with their CPUs.
Some of the fuel system failures that may need to be fixed to prevent limp mode include:
- Fuel Regulator Failure
- Faulty Fuel Pump
- Pinched or Clogged Fuel Lines
2. Clogged Air Filter Blocks Air Flow
The air intake box’s location varies by make and motorcycle’s year model. All combustion engines require an available air supply for proper combustion and throttle response.
Therefore, your air intake has a filter to prevent dust and debris from entering your machine through your air box. These air filters need to be cleaned or replaced per the specified intervals in your owner’s manual to keep your bike running smoothly.
If your motorcycle’s air filter is clogged up with dust and debris, the filter restricts the flow of air into your engine.
Air is as essential to a combustion engine as fuel is; a choked air supply causes engine performance and acceleration problems.
For starters, if the engine’s air intake is obstructed, you’ll notice a weakened or delayed response when you hit the throttle, which can cause it to shut off while riding.
Since starting the motorcycle requires less air, your bike may start back up only to die again when you start jamming on the throttle.
Since the airbox’s filter is blocked, your bike’s combustion chamber takes in more fuel to counteract the lack is air, causing a massive dip in your bike’s average miles per gallon as well.
Change or replace your air filter per the specified intervals in your motorcycle’s owner’s manual to keep the air/fuel mix even and prevent your motorcycle from stalling out while riding.
- Some motorcycle air boxes use reusable mesh alloy filters you can scrub out with warm water or degreaser, depending on the type and design of the filter and the instruction in your manual.
- Other bikes use disposable paper filters you can replace during routine service maintenance.
Suppose a blocked disposable filter is why your motorcycle shuts off while in motion, and you can’t get a replacement filter. Then you can use air to blow out the filter as a temporary solution. However, you’ll need to change your filter asap to prevent further engine damage.
3. Clogged Gas Cap Vent
If you had your motorcycle in storage for a while and now it stalls while riding even though it starts OK, there may be an issue with your gas fuel tank’s ventilation and airflow. This will likely happen due to a potential clogged fuel cap.
- As your bike’s fuel supply warms and cools due to changes in temperature, both inside the cycle and in your environment, it creates pressure inside the tank.
- The gas cap vent in your tank’s gas cap allows pressure to release.
- Gas cap vents commonly become blocked by moisture, dust, dirt, or debris after your motorcycle’s storage.
If you ride your motorcycle with a blocked gas cap filter, pressure build-ups in the tank as your motor dies while the fuel warms up.
The pressure slows down the fuel flow and causes the bike to stall out when you give it throttle, though it may start right back up once the fuel cools.
Clean out your bike’s gas cap vent, following the instruction in the service manual for its year model.
4. Fuel Filter Blocked By Mineral or Rust Deposits or Bad Fuel
While some bikes come stock with external fuel filters, most models have their filters inside the fuel tank.
While external filters are easier to replace, changing your internal tank filters requires removing the entire fuel tank.
On some used motorcycles, the previous owner may have installed an external fuel filter to bypass the filter inside the fuel tank.
Whether your bike uses an external or internal tank fuel filter, a clogged fuel filter is one of the most common causes of a motorcycle that shuts off while riding but starts back up.
A clogged fuel filter prevents fuel from entering your fuel lines. When you hit your throttle, your motorcycle will attempt to guzzle fuel through the blocked filter. At this point, it will cough, sputter, and die.
At start-up, less fuel is required so that the bike may fire back up.
Fuel filters get clogged with grime, rust, water, or mineral deposits in expired fuel and need to be cleaned often for peak performance. Mind you, it’s important to follow the spec outlined in your owner’s manual.
Make sure you also check out 9 known issues that make motorcycles to keep stalling.
5. Ignition Timing Needs Tuning
Modern bike motors equip multiple systems of moving parts that have to work concurrently. Your motorcycle’s ignition timing is a vital element of engine operation.
Advanced ignition timing causes a noticeable decrease in engine performance, including aggressive clanging noises. It can interfere with your motorcycle’s piston rotation, causing the bike to shut off while you’re riding.
Delayed or retarded ignition timing can cause your bike’s fuel to combust late while the piston is already on its way back up the cylinder, forcing it back down. The result is a motorcycle that shuts off when you hit the throttle.
- On modern motorcycles, ignition timing is maintained by the motorcycle’s Electronic Control Unit or ECU.
- If an ECU-regulated ignition timing fails, the ECU either needs to be updated (flashed) or the ECU is faulty and needs to be replaced.
Older bikes are equipped with a mechanical system of breaker points to control the motorcycle’s timing.
These points were arranged in a way that jolted the ignition coil at precise times.
In time, the point contacts wear down from use, slowly altering the ignition timing as they change shape. Eventually, your motorcycle will lose power under acceleration but will start back up OK.
To restore an older motorcycle’s ignition timing, your worn ignition breaker points must be replaced and adjusted correctly.
6. Erroneous Internal Engine Compression
As a combustion-powered machine, your motorcycle engine’s cylinder needs to be sealed to hold the compression and the momentum of your pistons.
If the seal between the cylinder bore and the piston rings is compromised due to an improperly seated gasket, the compression escapes from your engine.
Also, if your motor’s compression is compromised, the piston’s momentum is hindered, causing your bike to die. Throttling your motorcycle can push the air through the seals, making it more common for the bike to shut down while riding.
Inspecting your cylinder seals is part of routine maintenance and should be conducted by a familiar mechanic based on the spec in your service manual.
- The first step is to locate the faulty seal or gasket, restoring the proper compression.
- Once located, remove and open your bike’s motor and replace the faulty parts.
- If the compression is compromised because of a cracked cylinder wall of a faulty cylinder’s bore, the cylinder may require re-boring or repair to stop your bike from dying when in motion.
7. Faulty Ignition System
Inspecting your spark plugs and ignition coils is integral to routine upkeep on any motorcycle.
Your spark plugs and their wires are equally crucial to your bike engine’s combustion process. Because these components transfer electrical current, they wear out over time and must be replaced.
Your ignition coils must also be inspected and serviced regularly, per the intervals in your bike’s owner’s manual.
- Spark plugs should be inspected at the service intervals suggested in the owner’s manual by your moto’s manufacturer, and if your motorcycle stalls out while throttling.
- Also, inspect the connection between the ignition coil and the spark plug.
- Examine the condition of the ignition leads and the ignition coil.
- Replace any ignition system components if their integrity is compromised, as a weakened ignition system is a common cause of motorcycle stalling outs during acceleration.
Learn more about this by checking out our post on why motorcycle dies when accelerating.
8. Throttle Bodies Out of Adjustment
Modern motorcycles are equipped with fuel injection systems managed by a computer unit or ECU to deliver a specific air or fuel quantity to your engine.
This injection system includes throttle bodies that need to be balanced electronically. Throttle bodies are typically checked by a technician using a computer that connects to your bike’s ECU during routine tune-ups and adjusts your injection system accordingly.
If your motorcycle throttle bodies aren’t periodically adjusted, they can fail while you’re riding. This could cause the motorcycle to shut off, regardless of how well it fires back up.
There are capable wrenches that you can use to adjust your motorcycle’s throttle bodies. However, we suggest you see a pro on this.
Adjusting your injector system without a complete understanding of motorcycle mechanics can throw your throttle bodies further out of alignment and cause total engine failure.