This how-to guide will help you to test your motorcycle stator, identify common symptoms of malfunctioning and guide you to conduct tests to see if it needs replacing properly.
A motorcycle stator, not to be confused with a generator, generates the electrical power that the motorcycle needs for its ignition and charging systems to function. It converts the rotational force produced by the engine to DC (direct current) as an alternative power source for the battery. It is, therefore, critical for the motorcycle to be usable.
If the stator does not work, neither will the motorcycle.
What a Motorcycle Stator Looks Like and Where it is Found
The stator is found under the rotor or flywheel, usually under a cover on the lower left side of the engine. If in doubt, refer to the motorcycle’s manual to find the exact location.
It consists of wire coils or windings and contains magnets. When the rotor or flywheel rotates, the coils pick up the magnetic field and generate an AC current which then powers the motorcycle’s electrical system.
Stators are either single-phase (single coil), as in smaller motorcycles, or three-phase (triple coil), usually found in larger motorcycles due to the need for greater power.
Identifying Symptoms and Types of Tests
The typical symptoms to look for which could indicate a failed stator is the motorcycle not starting, the battery not charging, and no spark from the spark plugs.
Even if none of these problems are occurring, a worn-out stator could be reaching the end of its useful life. Inspect it thoroughly and look for any signs of damage in the wiring. Problems can also arise from electrical issues, poor ventilation, overheating, or there could be physical damage if the motorcycle was involved in an accident.
A proper test to check whether the stator is functioning requires using a multimeter.
You may also need to refer to your motorcycle service manual to know which range of values are acceptable because this can vary between different makes and models. The actual tests are of two kinds: static tests and dynamic tests.
A static test is conducted while the engine is turned off, and a dynamic test is performed while the engine is running.
A static test is sufficient if you want to check for any breaks in the coils, whether the stator is shorting to the ground, or if there is some other fault in the coils. The dynamic tests are done for checking the voltage.
In general, these are the main ways to test a motorcycle stator:
Static Tests
- STATIC TEST 1: The stator ground test
- STATIC TEST 2: The stator resistance test
- STATIC TEST 3: Crankshaft position sensor resistance test
Dynamic Tests
- DYNAMIC TEST 1: Testing for AC voltage
- DYNAMIC TEST 2: Testing for DC voltage
We’ll go into more detail below.
Static Tests for Checking a Motorcycle’s Stator
In all the static tests, ensure the ignition switch is set to the OFF position first, then set up the multimeter according to the type of static test.
Three basic static tests can be performed: (1) stator ground test or ohms test, (2) stator resistance test or insulation test, and (3) crankshaft position sensor resistance test.
STATIC TEST 1: The Stator Ground or Ohms Test
This test checks for any break in the coils and is done as follows:
- Set the multimeter to ohms.
- Disconnect the wire from the stator to the wiring harness.
- Connect the multimeter leads to two of the three terminals of the electrical connector in different combinations: 1 and 2, 1 and 3, and 2 and 3.
- If the test shows OL (Open Loop), it indicates a break somewhere in the circuit.
If a break in the circuit is confirmed, the stator has to be replaced.
STATIC TEST 2: The Stator Resistance or Insulation Test
This test checks if the stator is shorting to the ground and is done as follows:
- Place the multimeter’s ground probe to any nearby ground source.
- Attach the positive probe to each terminal of the stator’s connector in turn.
- If the multimeter does NOT show OL, it indicates some resistance.
If any resistance is confirmed, the stator must be replaced.
STATIC TEST 3: Crankshaft Position Sensor Resistance Test
This test checks for any fault in the coils and is done as follows:
- Set the multimeter to ohms.
- Disconnect the wire from the stator to the crankshaft position sensor.
- Test for resistance by connecting the multimeter leads to the terminals in the stator’s connector.
- The test should show some resistance within a certain range (check your service manual).
- If the multimeter shows OL, there is a break somewhere in the circuit.
If a break in the circuit is confirmed, the stator has to be replaced.
Dynamic Tests for Checking a Motorcycle’s Stator
The dynamic tests for checking a motorcycle’s stator are performed while the engine is running. Needless to say, they are only possible if the engine is able to run. Turn off all power sources, such as lights and radio, and let them run idle.
DYNAMIC TEST 1: Testing for AC Voltage
The first dynamic test measures the AC voltage from a coil to coil within the stator. It is conducted as follows:
- Set the multimeter to AC volts.
- Place the multimeter’s ground probe in any nearby ground source.
- Attach the multimeter’s positive probe to each terminal of the stator’s connector in turn.
- A reading should show for each terminal within a certain range, as specified in the service manual.
If any of the readings are below the acceptable range, then the stator has failed and it must be replaced.
DYNAMIC TEST 2: Testing for DC Voltage
The second dynamic test checks the DC voltage.
- Set the multimeter to DC volts.
- Locate the two wires next to each other on the ignition switch.
- Put one probe of the multimeter on these wires and turn the key to the ON position.
If no voltage shows, it indicates that the stator has failed and must, therefore, be replaced.
Final Thoughts
If all the above stator test results show that the stator itself is working fine, then you will need to look at other motorcycle components for the problems you are experiencing. For example, there might be a problem with the regulator or rectifier or fuel system, or there might be some connection issue. However, if there are signs of weakness in the stator or heavy wear and tear, it might still be a good idea to replace it because a bad stator can drain the battery. (1, 2)
Take a look at some of our related articles below.
- How to test spark plug with multimeter
- How to use a multimeter to test voltage of live wires
- How to check for battery drain with multimeter
References
(1) motorcycle components – https://www.sciencedirect.com/science/
article/pii/S0386111214601187
(2) fuel system – https://www.grc.nasa.gov/www/k-12/airplane/fuelsys.html
Video References
Fab Motorbikes
TheMotorcycleMD