Replacing the heater core on a Harley Davidson Knucklehead from 1940 to 1947 is a specialized task that requires a good understanding of the motorcycle’s heating system. click here for more details on the download manual…..

Classic 1947 Harley Davidson Knucklehead Motorcycle 1947 Harley Davidson Knucklehead In the early 1940s, Harley-Davidson introduced the Knucklehead engine, which became one …

Balancing and Installing a New Front Tire on a 1947 Harley Davidson Knucklehead The “Project Bike” is awaiting “stuff.” Therefore, we’ll take care of “who needs what?” The Knucklehead needs a new front tire, …

However, it’s important to note that classic Harley Davidson motorcycles, particularly the Knucklehead models, typically did not come with a heater core in the modern sense as you would find in cars. Instead, they relied on engine heat and some aftermarket accessories for warmth.

That said, if you’re referring to a custom setup or aftermarket installation that involves a heater core, the following is a general guide on how to approach such a task while keeping in mind the unique characteristics of the Knucklehead.

### Tools and Materials Needed

1. **Tools:**
– Socket set (including 3/8” and 1/2” drives)
– Wrenches (various sizes)
– Screwdrivers (flathead and Phillips)
– Pliers
– Hose clamps
– A coolant catch pan
– A torque wrench
– Shop towels
– Safety glasses
– Engine coolant (if necessary)

2. **Replacement Parts:**
– New heater core (specific to the custom setup)
– Replacement hoses (if needed)
– Hose clamps
– gaskets (if applicable)
– Any necessary hardware (bolts, nuts, etc.)

### Step-by-Step Replacement Process

1. **Preparation:**
– Ensure the motorcycle is parked on a level surface and the engine is cool.
– Disconnect the battery to prevent any electrical issues during the process.

2. **Drain the Coolant:**
– Place a coolant catch pan under the engine.
– Locate the petcock or drain plug on the engine and open it to allow coolant to drain into the pan. Ensure you dispose of the coolant properly.

3. **Remove the Existing Heater Core:**
– Identify the location of the heater core (usually mounted under the tank or within a custom fairing).
– Carefully disconnect any hoses that lead to the heater core. Use pliers to loosen clamps and gently pull the hoses off the core. Be prepared for some residual coolant to leak out.
– Remove any mounting hardware securing the heater core in place. This may involve unscrewing bolts or nuts.
– Gently pull the heater core out from its housing. Be cautious not to damage any surrounding components.

4. **Install the New Heater Core:**
– Position the new heater core in the same location as the old one. Ensure it is oriented correctly, matching the inlet and outlet locations.
– Secure the heater core using the original mounting hardware or any new hardware if necessary.
– Reattach the hoses to the new heater core. Ensure they fit snugly and use new hose clamps if the old ones are worn.

5. **Reconnect the Coolant System:**
– Close the drain plug or petcock to seal the coolant system.
– Refill the cooling system with the appropriate engine coolant through the radiator or filler neck. Follow the manufacturer’s specifications for the type of coolant to use.
– Start the engine and let it run for a few minutes to circulate the coolant and check for leaks around the new heater core and hose connections.

6. **Check for Leaks:**
– After running the engine, inspect all connections and the heater core for any signs of coolant leaks.
– If leaks are present, tighten hose clamps or adjust connections as necessary.

7. **Final Steps:**
– Reconnect the battery.
– Dispose of any leftover coolant and shop towels properly.
– Take the motorcycle for a short ride to ensure everything is functioning correctly.

### Important Considerations

– **Safety Precautions:** Always wear safety glasses and gloves while working on any motorcycle components.
– **Consult Manuals:** When in doubt, refer to the service manual specific to the Harley Davidson Knucklehead for torque specifications and detailed diagrams.
– **Professional Help:** If you’re unsure about any step, consider seeking help from a professional mechanic familiar with vintage Harley Davidson motorcycles.

This guide is a general overview and should be adapted to the specific configuration of your Knucklehead, especially if there are modifications or custom installations involved.
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