Starter keeps turning after I let go of the button

The starter keeps spinning after you release the button, often with a whine or grinding once the engine runs. The starter motor is meant to run for seconds only. Left running, it overheats within a short time, its cables can melt and catch fire, the battery is drained and the starter gears can be damaged. The usual cause is relay contacts that have welded shut, a start button that sticks, or a wire shorting to the relay coil.

Is it safe to ride?

No. Stop now. A starter that will not switch off is a fire risk.

Quick checks first

• Turn the key OFF at once. On most bikes this cuts the relay coil.
• If the starter still runs with the key OFF, the relay contacts are welded. Disconnect the battery negative (−) cable. Use gloves; the cables may be hot. Do not touch the positive terminal and the frame with the same tool.
• Smell for burning and look for smoke. If there is fire, move away and use an extinguisher, not water on fuel.
• Press and release the start button several times: does it spring back?

Diagnose it step by step

1Did the starter stop when you turned the key OFF?

• Yes: the relay coil is being fed by the button or a wire. Go to step 2.
• No: the relay's heavy contacts are welded together, or the heavy cable is shorting to the starter feed. Go to step 4.

2Does the start button spring back freely and does the switch housing stay dry and clean?

• No: clean or replace the switch. Clean a handlebar switch.
• Yes: go to step 3.

3With the relay's small connector unplugged and the key ON, is there voltage on the coil feed wire when the button is NOT pressed?

• Yes: a wire is shorting to the feed, or the button contacts are stuck. Find a short circuit.
• No: the fault is inside the relay. Go to step 4.

4Off the bike, do the relay's heavy terminals show continuity with no power on the coil?

• Yes: the contacts are welded. Replace the relay. Test the starter relay.
• No: check the thick cables for damaged insulation where the relay output could touch battery positive. Test the starter circuit.

5After the repair, does the starter turn freely and quietly, and the engine crank normally?

• No: the starter may have overheated or its gears are damaged. Remove and inspect the starter motor.
• Yes: charge the battery, it will be very low. See Test and charge a 12 V battery.

Why relays weld: long cranking with a weak battery, or a poor connection that makes the contacts arc. Fix the cause or the new relay will fail too.

Causes, most likely first