Motorcycle Repair: running hot in traffic, kawasaki ninja, radiator cap

Question
I have a 1986 Kawasaki Ninja 1000r with 25K.  When I'm in traffic the temperature spikes way up.  There is a switch to turn the fan on manually but it's not enough to cool the bike down.  I've replaced the thermostat, and the fan switch appears to be working fine.  When the bike is moving the temperature never goes above the halfway point on the gauge.

Answer
Hi Rob,

I suspect air is trapped in the cooling system.

Anytime the cooling system is opened or serviced, it needs to be purged of air. The cooling system is designed to be air-free. Air in the system causes the coolant to boil at a lower temperature. Serious engine damage may result if air becomes trapped at the water pump.

Air cannot be purges by simply bringing the engine up to temperature with the radiator cap off or by bleed valve.

Check on-line for a tool named AirEvac by Mityvac. Check the local auto parts stores for loaner tools.

Respectfully,
Mark Shively