Richard's ST2 pages - coolant

Information on this page last updated 08/17/01.

Here are some tips I have put together for coolant draining and re-filling, both seem to go quicker with the bike on the sidestand rather than the center stand:

• As with any vehicle, do not open the cooling system when hot.
• Remove the fairing panels. You might be able to do this job without removing all of them but it would be a real frustrating task.
• Open one of the drain plugs before removing the radiator cap. The coolant is kept in the overflow tank by the radiator cap. When you remove the radiator cap the overflow tank will start to drain into the radiator, and if the radiator is still full then it will quickly overflow and make a mess.
• There is a drain plugs on the coolant hose fitting on each cylinder head and also on the bottom of the water pump housing. They are simply small allen bolts with copper crush washers. All of these are on the left (shifter) side of the engine. I have had good results using just the drain plug on the horizontal cylinder, it is the lowest drain plug in the system.
• When refilling, you must first fill the radiator and then replace the radiator cap before filling the overflow tank.
• The shop manual says to add coolant at the radiator, wait for it drain into the engine, then add more coolant, and repeat until the radiator is full. I have found that this job can be done much quicker if you "burp" the system by squeezing the hose coming from the top of the radiator. You will get some air out, then can add more coolant to the radiator, burp more air out, and repeat until the radiator is full.
• The above may to 20 or more iterations as the system only allows a small amount to be added between burps. I found it convenient to clamp the overflow tank hose with pliers, fill the tank, and then let coolant into the system by releasing the pliers for a few seconds. This allows you to avoid repeatedly pouring small amounts of coolant in using a funnel.

A couple of other notes... I always use a non-silicate coolant as the ST2 has a plastic water pump impeller and silicates will likely accellerate wear. Several manufacturers make such coolant, like BMW and Honda. Whichever brand it should explicitely state that it does not contain silicates. I also use a bit of Red Line water wetter in my system and it seems to lower the average temperature a bit. That's a good thing in the Southern US :-)

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