83 & 89 Cooling issues...boiling..

[KIC]

Curious about an issue I have developed and then recently found out my friend who has an 83 is also dealing with. After riding for a while, even in cool weather when the temp gauge is not even ½ way, and I shut off the engine the water in the bottle is boiling. There is plenty of water, no leaks but it is not that hot yet. I am use to riding in Arizona temps in the summer where the temp gauge is just under the red line in city driving. In the winter it is ½ way.

My friend’s 83 seems to run under the red line in city riding even in the winter and boils when shut off. I guess we are going to do a clean out of the systems and he is going to change his impeller…but anything else we should be looking at ?

[M61A1MECH]

Check the radiator cap or sealing surface on the seat in the radiator. You can have the cap pressure tested to see if it is holding the correct pressure.

 

The coolant in liquid cooled motors does not boil because it is under pressure , that raises the boiling point, if the cooling system is not staying at the correct pressure when hot, the fluid will boil. If the pressure in the system exceeds the pressure the cap can hold the hot fluid will escape to the overflow bottle, that fluid is likely to still be hot enough to boil when it gets to the bottle.

[frankd]

On my 83, I had the same problem and found 2 things that were causing it. The first thing, was the radiator cap sealing surface leaking and the pressure never built up in the cooling system just like Steve said. In addition the cooling fan wasn't coming on. I found the connector on the switch that turns the fan on (behind the fairing, on the right side) had oxidized, and and wasn't turning on the fan. As i remember, the MkII bikes have different connectors for this. Let the bikes idle and see if the fans do run.

[KIC]

Both of our fans are working. But we both are going to get caps and see if that solves the problem. Isn't there a car radiator cap that works well that fits ? I think I had read that you have bend or remove a tab or something..

 

Is it best to just get a Yamaha over priced cap ?

[Condor]

Three things I can think of. Yep on the cap, two the thermostat, and three the drain valve is set on open. This will cause the coolant to bypass the thermo and circulate too fast and not transfer heat as efficiently. I used to add a little 'water wetter' to the coolant as well on my '83.

Edited April 22, 2016 by Condor

[bongobobny]

Just a FYI unfortunately on the MK1's the temperature gauge does read high, sometimes just under the red...

[frankd]

You can use a Stant 11227 or a 227. I found mine at Oreilly's and I had to grind one of the ears off so it could rotate properly.