Cooling fan runs all the time in city traffic

Quick question before everyone starts buying parts: when it happens, does the engine still crank normally and do the lights stay bright? That answer splits the problem in half.

Good point. I checked again: the lights stay on and the symptom is repeatable if I wait a few minutes. No smoke, no scary noises, just the bike being professionally annoying.

I would still check the simple stuff first. I once blamed half the motorcycle and it was a loose connector. The connector did not apologize.

Thomas Spagnoli: diagnose it like a mechanic, not like a gambler

This is a good real-world symptom because it sounds simple, but it can pull you into three systems at once if you let it. The trick is to slow down and make the bike prove where the fault is.

For "Cooling fan runs all the time in city traffic", I would use this order:

1. Coolant level and trapped air. Confirm it with a measurement or a repeatable observation before moving to the next step.
2. Radiator fins and airflow. Confirm it with a measurement or a repeatable observation before moving to the next step.
3. Thermostat behavior. Confirm it with a measurement or a repeatable observation before moving to the next step.
4. Fan switch or sensor reading. Confirm it with a measurement or a repeatable observation before moving to the next step.

Do not replace parts just because they are popular suspects. A weak battery, dirty connector, blocked pilot jet, dragging brake or bad ground can all imitate bigger failures. The boring test is usually the test that saves money.

If the problem affects brakes, fuel, steering, charging, or the engine cutting out in traffic, keep the test rides short and controlled. Safety first, pride later.

I am Thomas Spagnoli, professor and creator of the Motorcycle Mechanics Course. The course is free on this platform. Join it and use the lessons with these forum cases: you will learn how to split fuel, spark, air, compression, charging and chassis symptoms without guessing your way through the garage.

Thomas, that order makes sense. For the first check, would you test it immediately after the fault appears, or is it fine to test later in the garage after everything cools down?

Test it as close to the failure as you can. Some problems disappear when the bike cools down, which is very rude but also useful information.