Gl1100 running hot mystery?

[slickster]

1980 gl1100, doing the whole rescue, cafe racer thing, cannot get this thing to behave, it runs hot, within 5-6 minutes, the top of the radiator is 200 degrees, the bottom about 180, I had the radiator rodded out, removed thermostat, fan cycles, no excessive pressure when removing cap, no white smoke, waterpump impeller rotates, hoses good, runs smooth, it never boils over, the gauge nearly hits the red, checking temps with infrared thermometer....any suggestions?....my impression is that there isn't any coolant flow, for some reason...throw me a bone....thanks

[OldguyGlen]

Might not be any problem... need more info. No excess pressure, doesn't boil over, gauge 'almost" to the red, infrared showing 200 degree max... all that doesn't necessarily seem like trouble. Maybe your gauge just reads a bit higher than actual temp, and/or your infrared sensor too? These bikes run hottest when stopped and at idle. Does the gauge come down at road speed? Does the fan cycle on/off, or does it always stay on?
The temp sensor/gauge and fan thermal sensors are not precision devices. I recently changed fan switch and now my fan comes on way earlier than it used to, and the gauge reads much lower as a result. The engine is still happy at 200 degrees, even though that is a bit hotter than the typical thermostat opening spec. Just my opinion, we'll see who else has more info to offer on here.

[slickster]

Perhaps, I removed the thermostat guts, so it's as if it's always open, the needle is 1/32 away from the red, top of rad is 200 degrees, fan cycles, I can't believe it runs at 200 degrees, the coolant doesn't seem to be moving at all, just looking in with cap off....I expected it to run at 150-160 with thermostat disabled....I'll go for a spin tomorrow....

[Rambozo]

If the fan cycles on and off, it is running right where the fan switch is set for. You can pull the fan switch and test it with a thermometer and a pot of water to see if it's off. Removing the thermostat is not a good idea. It changes the flow rate and can cause weird heating problems. It sounds pretty normal for a stationary bike. How is it at highway speeds? There is a reason Honda didn't put numbers on the gauge, because then it would have to be accurate.

[DenverWinger]

How about your fuel gauge, is it reading higher than it should? Might be as simple as the 7 volt regulator is now giving 9 volts or something....

[mito57]

According to the service manual, the thermostat starts to open at 176 to 190 degrees and fully opens at 194. I don't believe you have a problem. This is a snip from the service manual.

[slickster]

So I took it for a spin....seems fine, temp gauge less than 1/2 way up, when I returned, bottom of radiator was 135, top 185....air bubble?...

[Rambozo]

That is typical. They need airflow to stay cool, and the fans only run when it's pretty hot. On the road it's no problem.

[DenverWinger]

plus - hot coolant flows into the top of the radiator - it's supposed to be cooler when it comes out the bottom.