Motorcycle Repair: coolant leaking, coolant leaks, coolant tank

Question
1984 honda FV700 interceptor. runs fine, BUT...when i shut it off coolant leaks out of an overflow tube in the back of the bike. Little bit of it leaks out of the radiator cap.  This ONLY happens when i shut it off, NOT when its running.  I can hear lots of bubbleing sounds from the engine. I just bought the bike, coolants looks new and clean.  Is it possible the that guy before me put in too much coolant? bike doesn't over heat, temp gage on the dash works fine. The needle moves up and down so i know the thermastat is opening and closing.  Don't know for shure if the fan works.

Answer
Tony, I would check the cooling system over for a number of issues:

Make sure that all the air is bled out of the cooling system. There is a fitting near the thermostat for that purpose, as I recall. I would probably change the thermostat anyway.
Check the coolant hoses to see if the bottom one that feeds the water pump isn't collapsing under higher speeds. DO verify that the cooling fan is working. Generally you can ground or jumper the cooling fan switch on the radiator with the key ON to test the fan function. If the fan doesn't come on, then the fan sensor switch is faulty.
The radiator may be corroded internally, causing reduced coolant flow through the system.
The coolant overflow tank should just be filled to the line and not completely full. The radiator should be full when checked at the cap (cold). If the coolant tank was over-filled, it would only overflow once or twice, then the level would self-adjust and the overflowing would cease.
Replace the radiator cap. It should not be leaking at any time, unless the pressure exceeds the cap rating. If it does, then there is a overheating issue that is occuring, despite the temperature gauge readings.

You might want to do a cooling pressure pressure check to see if there is any signs of head gasket leakage.

Finally there could be a water pump seal issue, so check the exact source of the leakage when you shut it down.

Depending on where you live, summer weather will aggravate the cooling system weaknesses, wherever they may be.

Parts illustrations are available at www.bikebandit.com and www.cmsnl.com sites, among others.

Bill Silver