Understanding/troubleshooting the safety switches
This article explains how the various safety switches on the EX250 work together and also gives some tips for figuring out if you have a problem with one or more of them. Please see the Electrical & Lighting section of the FAQ for other articles on the switches.
This is somewhat EX250-specific. Other bikes may have a different combination of switches and may work differently. Check their FAQ.
The components and how they work
The start circuit
For more assistance, see Start & Ignition Schematic.pdf
A bike can be started:
For everyone's safety, it's best to get in the habit of having your right hand on the brake when you thumb the starter.
To successfully start the Ninja 250, a number of conditions must be met before the starter solenoid can be energized. With the above schematic it is pretty simple to follow the path the electric current needs to flow, beginning with a fully charged battery.
Starting from the battery, the following conditions must be met:
At this juncture both the ignition module and the starter circuit relay are operational. Pressing the start button at this time will energize the starter circuit relay coil, allowing 12VDC to pass through the starter circuit relay to the starter solenoid.. When the starter solenoid coil is energized, the starter solenoid allows electric current from the battery to pass through to the starter motor, which in turn starts the motorcycle. Success!
The run circuit
However, success is short-lived, as the motorcycle cannot be driven at this time. Up to this point the ignition module connection to ground has been provided by a combination of the clutch lever safety switch position and the gear selector safety switch position.
The problem arises as the clutch lever is pulled in (clutch lever safety switch changes position - connects to ground), the transmission is shifted out of neutral and into gear (gear selector safety switch opens - no connection to ground), and the clutch lever is slowly released (the clutch lever safety switch changes position - connects to the gear selector safety switch), disconnecting the ground connection to the ignition module enable circuit and stopping the engine.
This is where the sidestand comes into play; with the sidestand in the down (parked) position, the sidestand safety switch is open (no connection to ground). When the sidestand is raised to the up (riding) position, the sidestand safety switch closes (connecting to ground) and completes the ignition module enable circuit, allowing the motorcycle to be driven. As the sidestand safety switch is only a component of the run circuit, and not a component of the start circuit, the position of the sidestand is not relevant when diagnosing starting problems.
Safety Switch Facts
To start the Ninja 250, both the clutch lever safety switch and the gear selector safety switch must be working correctly.
Troubleshooting the safety switches
For more help, see Start & Ignition Troubleshoot Schematic.pdf
Here is a quick method to trouble-shoot and eliminate the clutch lever and gear selector safety switches from the start circuit, in the event a starting problem arises. Unplug the clutch lever safety switch connector at the clutch lever, and temporarily install a jumper wire between the Black/Yellow (chassis ground) wire and the Black/Red (start circuit) wire.
With the jumper wire installed temporarily, the clutch lever safety switch has been bypassed, the ground to the starter circuit relay has been restored, and the ignition module enable circuit has been restored. If the motorcycle starts, then most likely one of the two safety switches is faulty. If the motorcycle still does not start, then the fault is not with either of these two safety switches. Remember to remove the jumper wire and reconnect the clutch lever safety switch connector when finished trouble-shooting.
Note of caution: With the safety switches bypassed, it is possible to start the motorcycle in gear, possibly running it into a passerby or out through the end of your garage. Use the centerstand to support the motorcycle while troubleshooting.
If the Ninja starts and runs, but dies when the clutch lever is released with the transmission in gear, here is a quick and simple trick to eliminate the sidestand safety switch from the run circuit. Remove the left-side panel and locate the two sidestand safety switch wires (Black/Yellow and Green/White) running alongside the chassis tube.
Temporarily disconnect the two sidestand safety switch wires (bullet connectors) from the wire harness. Then, connect the two wires from the wire harness to each other.
With the Green/White and Black/Yellow wires temporarily connected, the sidestand safety switch has been bypassed, and the ground to the ignition module enable circuit has been restored. If the motorcycle runs, then most likely the sidestand safety switch is faulty. If the motorcycle still does not run, then the fault is elsewhere. Remember to reconnect the sidestand safety switch to the wire harness when finished trouble-shooting. Failing to do so is very unsafe.
Before deciding to replace a safety switch, a quick inspection may turn up a misaligned switch plunger, or a buildup of road grime around the switch, preventing the switch plunger from fully extending. Frequently all that is needed is a good cleaning and a spritz of WD-40 for lubrication. Tempting as it may be to operate the motorcycle with the safety switches bypassed, DON'T. The safety switches perform two very important safety functions: