Solenoid chatter
When the starter button is pressed (key on, off/run switch in run mode), voltage is sent to the coil of the starter solenoid. If the system voltage is normal, the starter engages.
If the system voltage is low, due to low battery or faulty battery cables (the frame/motor end of the negative cable is a common issue), then the voltage may be sufficient to close the coil, but when it closes the high amperage contacts from the battery to the starter, the low voltage has a compound effect:
A. Lower voltage is a challenge to the starter turning over the motor and
B. Lower voltage results in a higher amp draw for the motor to try to pull the same wattage.
For example, a 1.4 KW starter draws 109 amps at 12.8 volts, 111 amps at 12.6 volts , 113 at 12.4 volts, 133 at 10.5 volts, etc.
In a low voltage condition, once the starter tries to draw enough amps to turn over the motor, the voltage drop is so excessive that the coil cannot remain energized and it opens the high amperage contacts to the starter. If the starter button is held, the voltage recovers (after the coil drops out) enough for the coil to again close and the cycle repeats until the voltage drop will not allow the coil to close. This is solenoid chattering.
If the voltage is very low, there is only one click and there is not enough voltage for the coil to again energize.
A huge amount of issues are caused by battery cable deterioration and/or loose connections, especially on the negative cable to the frame.
Whenever there is a problem that may even remotely be electrical, it would be helpful to post the following voltage readings:
1. KEY OFF battery voltage, at the battery: Normal is 12.8, acceptable is 12.6 (standard lead acid battery, not AGM) to 12.8 for no load. If just taken off a charger, voltage may be 13 point something. The battery needs to sit for a while before a reading is useful. In the case of a bad cell, the other cells overcharge and give an almost normal reading, until load is applied.
• If lower, then battery is discharged and needs charging or
• Battery has a bad cell
2. KEY ON battery voltage (headlight on): Normal is not under about 12.5 initially, but will decline the longer that the headlight is on, without the motor running. Under no load, 12.5 volts indicates 50% discharge, but under load, it is just voltage drop.
• If lower, then battery is discharged and needs charging or
• Battery has a bad cell or
• Battery cable(s) have high resistance
3. KEY ON battery voltage while cranking: Normal is not under 10.5 volts
• If lower, then battery is discharged and needs charging or
• Battery has a bad cell or
• Battery cable(s) have high resistance or
• Starter is drawing too much current
4. If the bike is running, battery voltage at about 2,500 RPMs should be 13.8 to 14.8
• If not, then check stator resistance and regulator ground
• If the stator is not shorted to ground and resistance is within spec, the regulator or regulator ground is suspect
