cooling questions on a k75c 38k from 1986 new to me

[tcroullier]

Simple questions while I am searching this Motobrick great resource

I am a 15+ year Airhead semi capable wrencher with tool but ignorant in matter of cooling. K75 Engine is encased in a Pischler fairing which while beautiful does not improve cooling. My right calf was read from the heat.

First 200 miles  small roads/Highways/ Chicago and the coolant liquid  starts squirting on my right leg. 200 meters from my home. No light signal on the dashboard, and no fan noise. Previous owner, reputable tells me the Fan was working recently.. Bike performs beautifully. I have the Haynes book which I am reading with great attention.

1) did I damage the bike?
2) my preliminary next steps are:
- look at fuse box
- investigate if cooling switch still works
-try to get the fan to run by shorting the relay
-Flush and look at the thermostat
Anything else?

Thanks and hoping to help others in the forum soon!

[frankenduck]

What's a cooling switch?

Probably just a bad radiator cap if it blows before the engine heat indicator in the cluster goes on. Been there, done that.

Radiator cap is part 17111464720

No, you did not damage the motor.

The cooling system works just like a car. Think of a K bike as a car on two wheels.

More here;
https://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/tempsensor/tempsensor.htm

[Laitch]

Welcome! Post a photo of your Brick. If the Brick performs beautifully—as you have indicated—it hasn't been damaged.

Before you undertake your list, go for a ride after the cap gaskets or cap are replaced. You can check fan operation and dry off your leg later, or wear a waterproof gaiter on that leg. The riding season and life itself are too short.

The fan starts before the over-temperature bulb lights up in the instrument cluster. When a fan starts operating, it does not indicate trouble. It's a thermo-regulation device designed to keep the engine at optimal running temperature.

[tcroullier]

thank you! here is a picture

[frankenduck]

The fan starts before the over-temperature bulb lights up in the instrument cluster. When a fan starts operating, it does not indicate trouble. It's a thermo-regulation device designed to keep the engine at optimal running temperature.

The thermostat opening, not the fan coming on, is what regulates the 'optimal' operating temperate when you're moving. The fan is only there to to push air through the radiator when you're stopped or moving very slowly and the coolant gets several degrees above the normal operating temperature of the thermostat.

[Laitch]

Thanks for the photo. Here's a link to a document from which you could get a few ideas concerning heat control.

The thermostat opening, not the fan coming on, is what regulates the 'optimal' operating temperate when you're moving.

The fan is part of the control system of heat management to optimize performance. Is there heat stroke happening out in K-landia? Get back under your shade tree. You're too valuable a resource to let your brain fry out in the open. Use a fan, fergawdsake!

[tcroullier]

Thank you to all. I followed advice, learned a lot about cooling, remove the fairing and will install a new fan as mine seems dead.

[Kaos]

It might also be worth to check if your radiator thermostat isnt ceased or gunked up. If it doesnt open your coolant wont run through the radiator and your bike will over heat
These (17111460716 ) can also be obtained in 3 different temperature values.

[tcroullier]

Thanks I will definitely check the thermostat but was able to run 700 miles back and forth in 2 days without the engine heating up. The radiator and and hoses were hot but not burning hot.

Could one ride a k75 for 700 miles in highway/small roads without water cooling?

[Kaos]

Depending completely on weather conditions. So technically yes. Likely no.
If i ride at low temperatures my engine wont go far over 80 celcius, but then mine is completely stripped.
And it is not without cooling, its without circulation trough the radiator. The temperature at which the the thermostat opens is still a temperature of liquid you wouldnt want running over your legs.
But. Having read all comments and carefully processed them the coolant squirt could also be a full overflow, bad cap , knicked or cracked hose.
Your fan should turn on at 103c (217f) and on overheating  the engine would be shut down
So there isnt much to worry about by the sounds of it.
Just some things to check.

[tcroullier]

Thank you very much Kaos and others. These were very hot days in the US Midwest so I am pretty sure the thermostat is functioning and the cooling works. I changed the cap, refilled the coolant and removed the lower parts of the fairing. The bike rides like a dream.

I know the fan is not functioning for sure.  I bought a new fan and when the season is over will replace the fan and check the thermostat by putting it in hot water. I really appreciate the help from all of you! These are great bikes.

[frankenduck]

Could one ride a k75 for 700 miles in highway/small roads without water cooling?

IL in summer? No.

[tcroullier]