Overheating 1991

I would say that you don't have a problem with the cooling system if it holds coolant in the overflow tank and it isn't going into the red. Usually thermostats fail in the open mode. You might try taking your thermostat out You can test it with a pan of water and a thermometer.

Is the fuse in the fan circuit good?

 

I must retract my previous statement - beta is the man; it was the cap. It's hotter than the last time I took it out, but it stayed within the nominal range specified by beta. However, my fan is still no-go. I'll have to give it a good inspection once I get back in town next week.

In other fun news, I blew two fuses simultaneously idling down the backside of a small hill ; the 10 amp ignition and the 30 amp starter relay back by the battery - completely dead just like that. Fortunately, I had a spare 30 amp in the fuse box and moved the 10 amp from the clock circuit (don't have one anyway) and it was like nothing had happened. Very strange. I wonder if this may be connected to my fan issue?

 

the fuses are a clue... (guessing now)... look for a chafed fan wire ... if not fan wire, something is grounding

 

The brass thermo switch on the radiator usually has the opening temp stamped right on one of the sides of the switch. It will be about 240º or so. That is 240º in coolant NOT water. You can put it (thermo switch) in some coolant on the stove and heat it up. Use a multi meter to see if it works. Make sure your meter probe does not touch ground of the metal pan or you will get a false reading.

Then see if the fan would work. Test below:

If it, ( thermo switch on the radiator) has one wire just remove the wire and touch it to ground, the fan should come on.

I would add the "new York City" on/off switch just to not have to worry so much.
Get control over that fan.

Sometimes the temp indicator pick up is on the radiator and sometimes it is on the thermostat housing. That makes a difference too.

 

Just a quick update this morning:

Finally got around to replacing the fan switch on the radiator last night. That was indeed the issue with getting the fan to run as everything seems to be good now. I took the opportunity to flush the system and switch to distilled water with Royal Purple's "Purple Ice" additive. We'll see how the performance of the cooling system changes I guess.

Also installed NGK Iridiums while I had nice and easy access to them. It looks like a ring job will be in my future this winter; the old plugs had a some amount of oil on them. Strangely to me, on the front two plugs the oil was liquid and on the back two it seemed to be burned carbon - not sure what that indicates. Now all I need to do is get the carbs properly in synch and slap the side fairings back on and this "little project - can I borrow the garage for a few weeks" (that was a year ago) will be finished!

 

awesome

keep an eye on the plugs, could be something as simple as dirty carb/running rich. throw 4-5 oz of seafoam in for a couple of tanks and regroup after riding season. Enjoy the Bike!

 

The thermo switch must be tested in a pan of anti freeze NOT water.
The temp of activation is stamped on the side if the switch.
Check with volt ohm meter to see if the switch opens. Don't let ground of the ohm meter probe touch the metal pan or you will have a false reading.

 

Piston rings! You did not even tell us the mileage!
Do a compression test PROPERLY before making a determination about replacing piston rings.

 

Don, where did you get this specious misinformation, and why did you, with all your experience believe it ??

I have 5 or 6 bad VFR/VTR thermoswitches in my parts bin, and all are stamped "100," which obviously means 100C. = 212 F. So fan is set to activate there, just at boiling point, but pressure in system--limited by radiator cap setting-- raises the boiling point in practice.

At 240F. it would be way too late to use the fan.

 

I'm holding my thermo-switch in my hand as we speak (I'm trying to find a cooler one), it is stamped "110-on" that equals 230F, too hot for my liking.

 

All the crapped out switches i've replaced over the years and thrown into the parts bin are marked "100".........110 makes no sense.

Do the manual switch; you'll be glad you did !