1990 K1 Heating/Cooling Question

[Terpster]

A question for all you knowledgeable folks out there. Last year on my summer holiday my K1 started overheating and I found that the fan was not coming on as it should be. I took it to a shop in Calgary as that was the closest to me. The fitted me in and did some troubleshooting and found that the fan relay was shot, it was replaced but the fan still did not come on. They also found that the rear seal was leaking and the clutch should be replaced as the oil had probably contaminated it. So with a sad look on my face, I left the bike there and headed home and cut my vacation short. Once the summer rush was over they started digging into my bike and found that the fan was not grounding once the temperature was reached to start the fan. This circuit goes into the motronic unit so a new one was needed or a switch put in place to make the ground. I got lucky and found a motronic unit on Ebay at a reasonable price, so the deal was done. Got the bike home on the 23rd of Dec with a new clutch, rear seal and the fan working. I have now noticed that the bike heats up very quickly, more so than it used to. All it takes is one red light to make the fan come on. Also it now takes much more clean air while driving to cool down the coolant temperature that it used to. The fan used to be able to draw in enough air to cool the bike so that the fan would cycle off, not anymore. Any ideas on what could make the bike heat up so quickly and why the fan won't cool it down anymore on it's own? Thanks.

 

[98lee]

I know this is going to sound dumb, but are you SURE the radiator is full to the top of the fill cap (under the front of the tank)? Not just the overflow bottle. A cracked overflow hose from the radiator to the overflow bottle will pump coolant out of the radiator and suck air back in.

Also check your fuel filter. Could be plugged causing a lean condition.

If that is ok, you might want to swing by a shop with an exhaust analyzer. It could be running too lean. Could be problem with the Motronic or O2 sensor.

 

[TMCKRS4V]

K Kooling..

My 91 K100RS 4V was having similar issues a year ago after I had replaced my cooling fan motor + coolant renewal. (New OEM Bosch from BeemerBone yard).
The fan would come on but the temp gauge would climb tword the red in traffic. I was convinced that the thermostat was history till I pulled and tested it on the stovetop in boiling water and a thermometer. I was actually dissapointed when the thing opened @ 180F like it is supposed to. Finally "burped" the system... got it back together...all OK. BTW use caution around the coolant plug/temp sensor. VERY soft brass... don't know how I managed to shear the thing ..but I did. That special order item plug was like $30. Have not replaced it... but will with the "Post-Redmond" oil change. (Think it calls for 7ftlbs) Bike will turn 100K very soon. (Second DS + Trans..but that is another story)

 

[bmwwrench]

I hope that some of your problems are due to miscommunication with the shop that repaired your bike. The Motronic provides a ground signal to the fan relay to power the fan. The fan is not grounded to the Motronic.

At any rate, the problem you are having with the fan running so often and so much is probably a lack of coolant. The K1 has one unique hose in the cooling system which makes filling the system difficult. The motor must be run until the thermostat opens and all air rises to the top of the system. Unless this is done, the system will be only partially filled, with the results you are experiencing. You'll have to pull the tank back and top off the system.

They may have also put in a stronger concentration of glycol than optimal. Check the coolant strength with a hydrometer and if necessary, dilute it with water, preferably distilled. To help cool the motor, you might also add Redline "Water-Wetter" or one of it's competitors.

 

[Terpster]

Thanks

Thanks for the suggestions, I will give them a try and see what happens.

 

[Terpster]

Heating/cooling

Well I let the bike run with the radiator cap off and let it cycle the fan off and on a couple of times. I got a few bubbles out of the coolant and topped it off with more coolant. It now runs better, it will heat up still quite fast but now the fan will lower the temperature so that the fan cuts out. I guess next I will test and possibly replace the thermostat. Thanks for the help.