Join Date: Sep 2018
Location: West Coast Florida
Three tips from my experience...
1) Pull the plastic shroud off the front of your radiator and inspect the radiator fins. If you ride on gravel roads at all like the previous owner of my '85 VT700C did, the front fender does not extend down far enough to protect the radiator from stone damage. Mine was beat to a pulp. Though not leaking, the fins were damaged beyond repair, clogged with dirt, and shutting off the air flow.
2) Pull your radiator cap off with the engine cooled down and make sure it's full. Pull your plug wires off to prevent firing, and crank your engine. If you hear huffing air coming out the radiator fill, you have a blown head gasket. A blown head gasket near an exhaust valve will force cylinder air into the cooling system, over-pressurizing the system and blowing your coolant out. You can confirm it with a compression test..should have 150psi + on each cylinder.
3) Look for a coolant drip underneath the left side of your bike when it is parked. On mine, the rubber nipple that connects the overflow tube from the radiator to the reservoir was cracked from age. Over time you can lose enough coolant from "normal" radiator overflow to cause overheating and filling the reservoir. You can inspect the nipple by removing the left fairing "Shadow" cover and then swing-out the plate with the stator wiring and looking at the coolant reservoir entry nipple. Wiggle the overflow hose to see if the rubber grommet on the nipple is cracked.
If it jams, force it. If it breaks it needed replacing anyway.