Motorcycle Repair: High temp, mity vac, temp guage

Question
Hi Mark,
I have an 87 1000R ninja which I've owned for 15 years. 21,000 on the clock. It's been a great bike with very few problems and is very well maintained. lately, the temp guage rises quickly even if idling only for a very short time. The fan kicks on and it does drop to the halfway mark.
While cruising or just riding around it stays in the cool zone with no problem. Sometimes the guage will rise and fall while just riding around.The bike has had regular coolant fills and flushes. Do  have water pump going bad?
Thanks in advance for your help.
Gary,
Tampa, Fl

Answer
Hi Gary,

I owned the 1986 1000R, painted her lime green and black. Kept the black parts black, red parts painted green.

I suspect there is air trapped in the cooling system. The water pump is working. Cooling systems must be air-free. Air causes the temp to raise. Coolant boils at about 235 degrees with 50/50 ratio in an air free system. Air lowers the boiling point. Air pocket at the water pump will cause problems such as you described.

Look at this tool by Mity-Vac. Its called the Air-Evac:

http://www.jcwhitney.com/webapp/wcs/stores/servlet/EndecaControllerView?D=mityva...

This tool may not be practical for the average guy's garage, but is mandatory when draining or filling the cooling system. Many shops don't use the tool. They have customers returning with problems.

That's what I think.

Respectfully,
Mark Shively