Q: I have a 1984 Honda VF700 Sabre that runs pretty hot, almost always toward the upper end of the temperature scale when not moving. It gets close to the point of overheating when the fan comes on, and has on occasion expelled coolant out of the overflow tubes. It also gets around 33-35 mpg, though everything I’ve read suggests fuel economy should be in the low-to-mid 40s. I don’t ride it aggressively enough to lead to this significant drop in fuel economy. Any thoughts?
A: You don’t say when your 29-year-old motorcycle’s cooling system was last serviced, but there’s no putting it off now. Start with the easy stuff. Clean the radiator by using a wooden toothpick to pry debris out from between the cooling fins. Look at the ground under the bike for signs of coolant leaking out of the water pump, and replace the pump if you see any. (V-four Hondas of this vintage are somewhat notorious for water-pump failure.) Check and clean the electrical connections to the cooling fan. Dirty leads could delay the fan coming on.
If none of this does the trick, drain the coolant. Remove the thermostat, and check it and the radiator cap. The thermostat should open at the temperature specified in the manual, and the cap should hold the specified pressure. Replace either if it’s not up to spec. Fill the cooling system with fresh coolant, and make sure you purge the air from the system. If your bike still runs hot according to the gauge, the gauge or the gauge sensor might be faulty. Finally, a bike this old might have blocked passages in the radiator, hoses, or water jacket, which could mean a complete teardown.
As for your mileage issues, you don’t mention any problems with idling, acceleration, or stalling, so it’s unlikely your carbs are the culprits. Pull the spark plugs and see how the firing ends look. If they’re coated with dry, black soot, check the air filter and replace it if necessary. Make sure there’s nothing blocking the airbox intake. You might also want to check the source of the mileage figure you think you should be getting. A lot of variables affect mileage, but yours sounds average for the year and model.