1985 Honda Interceptor 700 overheats on idle in stopped traffic

I have a 1985 Honda Interceptor 700 in excellent shape with only 19,500 miles. It runs smooth and cool while riding but if I get stopped in heavy city traffic it will overheat into the red. I have checked the coolant and added 50/50 mix. Should I replace the thermostat to see if that solves the problem? The radiator fans seem to be running fine. Thanks for helping out!

 

replace thermo and see if that works-I don't know much about a 700:juggle::spit::lever:

 

Does the fan kick on before the bike overheats? Or does the bike overheat at idle even if the fan is running?

Do you have a coolant pressure tester? Those are very helpful tools, especially with eliminating the radiator pressure caps as a potential problem. I've tested a bunch of these and found that many are bad, even relatively new ones. Some local part shops (AutoZone, O'Reilly's, etc.) will rent them to you.

If the rad pressure cap won't hold 13psi for a few minutes, our bikes will overheat. Many Asian auto makes used the same type of cap throughout the 80s & 90s (small deep bayonet type). I tend to pick up a few Asian make rad caps every time I'm at a pick-n-pull. Just be sure you get something close to 0.9 bar. I don't think 1.1 bar (15psi) would hurt anything, but 1.3 or 2.0 bar (30psi) might generate a bit too much pressure.

Do you have any leaks from the coolant manifolds (running under the carbs)? Those o-rings eventually wear out. How about evidence of coolant leaking from the water pump bleed hole? Any evidence of coolant in the crankcase oil or milky residue under the oil fill cap?

 

I didn't use glycol anti-freeze in my 83. Glycol will hold the heat in compared to water. I used distilled water, WaterWetter and rust inhibitor. I also had a manual fan switch to turn the fan on when I entered city/slow traffic areas. Being able to turn the fan on before heat soak was the best thing for it. I also run the same setup on my Blackbird and it works great.

IMO turning the fan on at 215* or so is kind of useless because the motor will get in to heat soak at times and it will be hard to cool from there or higher temps. Some guys don't consider 220* hot. It is IMO. the best temp for an ICE motor for power and fuel efficiency is between 180* to 195* max. I don't like to run motors hot, it takes it's toll over time.

Add a switch. Just tap in to the ground side of the temp switch, to one fan switch leg then the other leg of the switch goes to ground. The temp unit has power on one leg and ground on the other, so make sure you tap in to the grond side.