Identify Harley Davidson Engine Numbers On A 1966 Sportster

Newer Harley-Davidsons carry VINs on the frame and engine.

Whether a Harley-Davidson Sportster is right off the showroom floor or a 1966 Classic model, having the vehicle identification number is mandatory in the United States if buying or selling the bike. Because VINs were not also stamped on frames until 1970, there’s no sure way to prove the engine on an older Harley is original to the bike. However, identifying an authentic ’66 Sporty engine is pretty straightforward, as the VIN is easily accessed and contains only eight or nine characters. The only real effort may be to give it a quick wipe with a shop rag.


1. Locate the VIN on the left side of the engine. It is stamped on the case where the cylinders meet at the bottom of the “V.”

2. Verify the year the model was manufactured by checking to make sure the first two numbers are “66.”

3. The year will be followed by XLH or XLCH, the actual model of the bike. Each model had 55ci (883cc) V-Twin “Ironheads,” so named because the cylinder heads on these models were cast iron. Other models of the era were made of aluminum.

4. Check the last four to five numbers of the series, which identify the manufacturing run. The first of these numbers should be an even number, as the bike was built in 1966. In the case of a five-number production run, the first two numbers should be even numbers.