Before spending money on new parts, it’s usually worthwhile to do some testing to identify the root cause.
This guide covers troubleshooting the entire ATV starting system circuit, including testing the starter motor and the starter solenoid.
What Are the Components of the Starter System Circuit?
The starter circuit consists of these main components that all need to work for the ATV to start:
- Key Switch / Starter Button
- Starter Solenoid
- Brake switch / Neutral Switch /Clutch switch
- Start Diode
- Starter Motor
- Wiring and connectors
When the starter behaves strangely or doesn’t work, all of these components are on the list of possible suspects.
Many modern ATVs have non-serviceable starter units with a protective coating that will lead to premature component failure if removed. If your testing verifies that the starter is bad, you should replace the starter motor and solenoid assembly.
However, some starters are serviceable and can be disassembled for cleaning or replacing worn-out brushes.
Guide: How to Test an ATV Starter and Solenoid
The best way to test an ATV starter and starter solenoid is through a process of elimination, beginning with the smallest effort items and working your way through the circuit until you identify the culprit.
Often you will find that the starter unit works fine, but there is an issue with one of the supporting components, preventing the starter from operating normally.
To narrow down your search, you can note how the starter behaves when you try to start the ATV.
The Starter Motor Does Not Run
- If the starter makes no sound and does not run, there might be a problem with the starter or the starter solenoid, but there might just as well be an electrical problem preventing the starter from getting battery power.
- If the starter solenoid clicks but the starter does not run, you might have a faulty starter motor or a seized engine.
- If the starter solenoid makes a chattering noise, your battery may be low on voltage.
The Starter Motor Run but Turn Over Slowly
- If the starter motor turns over slowly, you know it is getting power, but there might be a low voltage due to a discharged battery or poor wire connections, worn starter motor brushes, or a binding ATV engine.
The Starter Motor Runs, but the Engine Does Not Rotate.
- If the starter turns, but the engine does not rotate, it is probably a mechanical issue with the starter gears.
Depending on your findings, you might be able to skip one or more of the troubleshooting procedures as outlined below.
Caution: Always wear eye protection when working on the electrical system.
1. Check the Battery and Battery Connectors
Before you do anything, ensuring the battery is in good condition and holds a sufficient charge is a good idea.
Use a multimeter to read the battery’s state of charge.
If the battery voltage is low (below 12.4V), give it a proper charge to eliminate a low voltage condition from the list of possible causes.
If you suspect your battery is going bad, here is how you can test the condition of the battery.
Also, ensure the battery terminals are on tight and not corroded or damaged.
2. Ensure the Solenoid Gets Power
The fastest way to eliminate or identify an electrical issue is to test for power at the solenoid battery terminal and ignition key terminal.
Locate the Starter and Starter Solenoid
The starter is cylinder-shaped, about 3×5 inches big, and connects to the engine on either side by the flywheel.
Often you need to remove a plastic side cover or the seat to get to where the starter and solenoid are mounted.
There are two main types of starters, and ATVs use both.
- An inertia starter has the solenoid mounted separately and away from the starter.
- A pre-engaged starter had the starter solenoid mounted on the motor casing.
The easiest way to find a separately mounted starter solenoid is to start by the positive battery terminal and trace the biggest wire down towards the starter.
Test for Power on the Solenoid Battery Side Terminal
The solenoid typically has two large terminals and one or two small terminals. The terminals and connectors are usually covered by rubber boots.
- One of the large terminals connects to a read, heavy gauge cable from the positive battery terminal.
- The other large terminal connects to a black, heavy gauge cable that connects to the starter.
- The small terminals connect to the key switch and control solenoid operation.
- The entire circuit grouds through the starter base to the frame and back to the negative battery terminal.
The solenoid battery side terminal should always have power. The solenoid ignition key switch terminals should have power only when pressing the starter button.
Before you begin testing, ensuring your test light is working is a good idea. Connect the test light alligator clip to the negative (-) battery terminal and put the test probe to the positive (+) battery terminal. The test light should come on.
To test for power on the solenoid, leave the test light connected to ground and put the test probe to the solenoid battery cable terminal. The test light should come on.
If the test light did not come on, you likely have a dead battery, loose, damaged, or corroded battery terminal connectors, or damaged battery cables.
Test for Power on the Solenoid Ignition Switch Terminal
Leave your test light or multimeter connected to ground and put the test probe to the solenoid ignition key switch terminal.
Press the starter button. The test light should come on, indicating that the key switch circuit works.
Suppose you don’t get power to the key switch terminal. You probably have loose or damaged key-switch wiring or a faulty key switch, starter button, transmission (neutral) switch, or starter diode.
Check the wiring between the solenoid and the ignition switch for continuity using a multimeter to identify any breaks in the wiring.
Test the various switches for continuity as well to ensure they work.
The starter diode is like a one-way valve in the starter circuit. You likely need a vehicle-specific wiring diagram to see where it is located.
Use a multimeter to measure between the diode connections. Continuity should flow only in one direction.
3. Test the Starter Solenoid
Inside the solenoid is a plunger operated by an electromagnet.
When pressing the starter button, a small current activates the electromagnet that shifts the steel bar, connecting the two large solenoid terminals.
When releasing the starter button, the electromagnet shuts off, and the spring moves the steel bar to its normal position, away from the two terminals, to break the circuit.
- To test if the solenoid delivers current to the starter motor, put the test light probe to the starter side solenoid terminal.
- The alligator clip should be grounded to the battery negative terminal or the ATVs frame.
- Press the starter button with the ignition switch in the RUN or ON position.
- The test light should come on, and the solenoid should sound an audible click.
- The test light should turn off when releasing the starter button.
The click sound you hear when activating the starter is the electromagnet shifting the plunger.
If the solenoid gets power but does not click, it may be faulty or seized due to internal corrosion.
To verify a faulty solenoid, you can use a screwdriver or a heavy gauge cable to bridge the two large solenoid terminals briefly. Bridging the terminals should cause the starter to turn.
Caution: Ensure the ATV is in park (P) or neutral (N), and wear safety glasses to protect you from the sparks. Use a heavy gauge screwdriver with an insulated handle and be careful not you touch any metal parts, including the screwdriver shaft.
If there is current on the starter side of the solenoid, but the starter does not turn on, the starter motor might be faulty, the ATV engine might be seized, or the starter circuit might have poor grounding.
A voltage drop test as described below, can help very an internal connectivity problem with the solenoid.
4. Tap on the Starter to Free Stuck Brushes
A quick way to test if the starter brushes are sticking in the brush holder or beginning to wear out is to gently tap or bump the starter housing while pressing the starter button to see if this frees it up.
The wooden handle of a hammer or a plastic or rubber hammer works well for this test. Do not hit the starter housing too hard or with anything metal, as the aluminum housing can easily crack.
Often you’ll find that this helps the starter kick in, and the ATV will start as normal. However, this is only a temporary solution. What caused the starter to turn is still there and needs to be identified and fixed for a permanent solution.
5. Do a Voltage Drop Test to Find Poor Connections
A voltage-drop test can help identify poor connections or excessive resistance in an electrical circuit.
Poor connections or excessive resistance anywhere in the starter circuit can prevent the starter from working.
The test sounds complicated, but it becomes relatively straightforward when you understand how it works and what it tells you.
When troubleshooting a starting circuit, we typically voltage drop test the following parts of the circuit:
- The power side of the starter circuit (positive side).
- The ground side of the starter circuit (negative side).
- Across the starter solenoid.
To do this test, you’ll use a multimeter set in the 20V DV setting, connected in parallel with the part of the circuit you’re testing (for example: from the battery to the starter solenoid).
When the starter is not engaging, the circuit has no load, and the meter should read either 0V or 12V (battery voltage).
- 0V when testing either the positive or the negative side of the circuit.
- 12V (battery voltage) if you’re testing from the positive side to the negative side of the circuit.
When activating the starter and the circuit is under load, the meter will read the difference in voltage between the two test leads. All wiring has some resistance, and a difference up to 0.3V is acceptable.
If you read more than 0.3V, an issue in the circuit prevents it from handling the current.
Move the lead up the circuit one connection at a time until the value drops below the 0.3V threshold. Once the value changes, you’ve isolated the problem area and can inspect and repair the issue.
The test can be used to test any part of an electrical circuit. Always put the test leads directly to the terminals and not on the connectors or exposed wire for a good result.
Voltage Drop Test the Power Side of the Starter
- Put the red lead on the positive battery terminal.
- Put the black lead on the solenoid battery side terminal.
When the key is off (no load), the meter should read 0V. When activating the starter, the meter should read no more than 0.3V.
Voltage Drop Test the Ground Side of the Starter
- Put the red lead on the starter ground. Some starters ground through a cable. Other grounds through the case.
- Put the black lead into the negative battery terminal.
When the key is off (no load), the meter should read 0V. When activating the starter, the meter should read no more than 0.3V.
Voltage Drop Test Across the Solenoid
- Put the red lead on the solenoid battery side terminal.
- Put the black lead on the solenoid starter side terminal.
When the key is off (no load), the meter should read 12V (battery voltage). When activating the starter, the meter should read no more than 0.3V.
6. Ensure the ATV Engine Rotates Easily
When a mechanical issue causes the ATV engine to seize or prevents it from rotating freely, the starter motor might not have the power to turn the engine. You might hear a buzzing sound from the starter motor when you press the starter.
If your ATV has been sitting or you don’t know the motor’s condition, this issue might be worth looking into.
Testing typically requires some disassembly to access the flywheel to the crankshaft. You should get a vehicle-specific service manual if you decide to do this at home.
7. Inspect the Starter Motor Gear and Starter Drive
Remove the starter from the ATV to inspect the gears for wear or damage.
This is how you remove the starter:
- Remove any plastic side panels covering the starter.
- Disconnect the negative (-) battery terminal.
- Ensure the area around the starter is clean.
- Disconnect the battery cable and key switch cable.
- Remove the bolts retaining the starter.
- Remove the starter from the crankcase housing.
On some ATVs, the starter pinion gear engages directly with the flywheel ring gear, called the drive coupler.
Other bikes, typically older or budget-friendly models, use a bendix starter gear to engage the starter with the engine.
Damages to look for:
- Stripped pinion gear, bendix gears, or flywheel ring gear.
- Faulty or loose bendix starter gear.
- Free-spinning flywheel gear caused by a sheared flywheel key.
- Flywheel loose or out of position.
8. Bench Test the Starter and Solenoid
To better understand how your starter sounds and behaves, you can test its operation on your workbench.
You will need a fully charged battery, jumper cables, and alligator clip test leads.
Caution: Remember to wear safety glasses and to keep clear of the starter pinion gear.
- Connect a black jumper cable lead from the negative (-) battery terminal to the base of the starter casing.
- Connect a red jumper cable lead from the positive (+) battery terminal to the solenoid battery side terminal.
- Connect an alligator clip test lead to the solenoid ignition switch connector.
- Grab the starter motor firmly with one hand at a safe distance from any moving parts to keep it in place. As a safer alternative, you can place the starter in a vice, but don’t overtighten it, or you’ll damage the aluminum housing.
- With the other end of the alligator clip test lead, briefly touch the positive jumper cable to engage the starter.
- Observe that the starter spins freely and that there are no strange noises like grinding or signs of dragging. Ensure the pinion gear moves in and out, depending on the starter type.
- Disconnect all cables when you are done testing.
Also, measure the resistance of the copper windings inside the starter.
- Put the multimeter to ohms/resistance.
- Put the red lead on the solenoid starter side terminal.
- Put the black lead on the starter base.
- The resistance should read around 0.1 ohms.
- The starter motor is faulty if the meter reads 1 or OL (overload).
The Bottom Line
Testing an ATV starter and starter circuit may seem overwhelming at first, with so many things could prevent the starter from working properly. But, by applying the systematic approach outlined above, I hope you managed to identify the root cause of your starting problem.
If you could not find a problem with the starter, maybe you missed one of the many other possible causes that can prevent an ATV from starting.