This is an Ironhead engine on a 1980 Harley Sportster.
Ironhead Sportsters, like your 1980 1000cc model, are notorious for overheating. Oil coolers work by providing additional oil in your system and an additional surface from which heat can radiate. Almost any oil cooler will work on an Ironhead engine as long as you understand the oil line routing on the motorcycle. In a 1980 Sportster with an after-market inline, as well as a drop-in, oil filter, the oil pump is fed by gravity from the oil tank. Oil pressure from the pump pushes the oil to the oil filter in-port. The oil then flows under pressure from the filter out-port to the oil cooler in-port, and from the cooler out-port to the oil tank return.
1. Drain the oil from the oil tank through the drain hose into a pan. Use a screwdriver to loosen the hose clamp. Remove the drain plug with a pair of pliers if the oil is hot. Remove and clean the drop-in oil filter.
2. Reseal and replace the drain hose. Spin off the in-line oil filter, if your Sportster has one, with an oil filter wrench. Drain the filter into the pan. Clean up any spilled oil with shop rags.
3. Disconnect the filter out-line from the filter out-port by loosening the hose clamp with a screwdriver.
4. Replace the filter out-line with the cooler in-line. Tighten the cooler in-line to the filter out-port with a hose clamp and screwdriver.
5. Bolt the oil cooler mounting clamps to the left down tube or both frame down tubes as specified in the instructions that came with your oil cooler. Use a box wrench or an open-end wrench to mount the clamps.
6. Bolt the cooler to the mounting clamps with a box wrench or an open-end wrench. Ensure that the cooler is facing forward and tighten the mounting clamp fasteners, as specified in your oil cooler documentation.
7. Attach the oil cooler in-line to the oil cooler in-port using high-temperature gasket sealer, a hose clamp and a screwdriver.
8. Disconnect the oil tank return line from the return line port. Discard the return line.
9. Attach the oil cooler out-line to the oil tank return port using high-temperature gasket sealer, a hose fitting and a screwdriver. Attach the oil cooler out-line to the oil cooler using high-temperature gasket sealer, a hose clamp and a screwdriver.
10. Check all hoses for kinks and bindings. Hand-tighten a new in-line air filter to the in-line oil filter fitting. Add four quarts of oil to the oil tank. Replace the drop-in oil filter.
11. Start your Sportster in neutral and allow it to run until warm. While the Sportster is running, check all hose fittings for leaks. Make sure the oil cooler becomes warm to the touch.
12. Turn off the bike. Check the oil in the oil tank and add oil as needed.