K1 1992 with cooling issues

[mlynchK1]

Looking for some advise on a k1.

 

The motor is overheating. I tested the electrical system and found that the fan motor is fine, the fan relay is fine, but when I jump the coolant temp sensor the fan wll not run. Is the MCU the problem?

 

Mike

[Dennis Andress]

Fan is fine...

 

I replaced the fan in my 91 a couple of years ago and found that the temp needle fell faster after the new fan came on. Before it died the old fan was running fine but still turning slower than it should have been.

 

 

I'm not sure what turns the fan on but it doesn't come on until the temp needle is almost in the red. This is the point when the thermostat is completly open. The temp sensor at the bottom of the water pump just drives the guage. The one the MCU looks at is behind the radiator. You'll have to remove the radiator to get access to it. I don't think jumping the coolant temp sensor is the way to go. A better way of testing would be to remove the temp sensor and but it in a pan of boiling water. The sensor is expensive but replacing it made a dramatic improvement in the way my bike ran.

[duckbubbles]

Hi, Mike-

 

Read your thread and thought of a couple of things to check. Get to the radiator cap, cold, and take it off. The water/antifreeze solution should be visible. If not, the cap could be bad, or the hose to the expansion tank could be bad. The level in the expansion tank should change between hot and cold, maybe 3/8 inch. If it doesn't, the cap/hose could be having problems.

 

The bike will heat up quite quickly in hot weather when sitting still or just trolling along slowly. Picking up the speed should cool it back to normal fairly quickly.

 

Water is a better heat conductor than ethylene glycol (antifreeze). I run a 25-30% glycol to 70-75% water in mine. In Texas and kept in the garage, I don't worry about freezing.

 

Frank