What Is Harley Davidson Engine Number & Where To Find It?

Harley Davidson engine number is a string of letters and digits that contains valuable information about your motorcycle. You can use this number to get information about its model, year, manufacture site, displacement, and similar specifications. 

This information is crucial when you are looking to service your Harley Davidson. It helps you identify the proper parts for the engine. Plus, you can verify the manufacturer’s originality. Learn more from the following discussion. 

Where Is The Harley Davidson Engine Number Located?

You won’t find the Harley Davidson engine number in the same place on all vehicles. Especially in the older models, the location varies greatly. The very first models didn’t even have an identification number for the engine. 

However, Harley Davidson became more consistent with their engine numbers after the 1980s. We owe that to the establishment of various strict transportation laws. 

Therefore, HD motorcycles after 1981 have a specific location for the engine number. It is inscribed on both crankcase halves (left and right). 

Meanwhile, Harley Davidsons from 1970-80 have the number on the engine block’s left side. Models before the 1970s show the inscription on the left side of the engine case.

Read Also: What Are Harley Davidson Torque Specifications? [Updated Info] 

How To Decode Harley Davidson Engine Numbers?

Decoding the engine number of an HD motorcycle is somewhat tricky. For instance, common knowledge is that it’s a 10-digit number. 

However, some models have a 17-digit engine number mirroring the VIN. Meanwhile, in some cases, the number can be shorter than 10 digits. 

Such inconsistency isn’t unusual for a company that has been manufacturing motorcycles for over a century. 

And the solution is to use the following breakdown not as a strict decoding but as a helpful guide- 

  • The first character is a number that tells you where the bike was made. “1” indicates inside the U.S. Anything else indicates a foreign make. 
  • The 2nd and 3rd characters are HD, which tells you Harley Davidson is the manufacturer of this motorcycle. However, the first three characters might not be present in some engine numbers. In that case, it starts with the fourth character.
  • The fourth character is a number that indicates a weight class. “1” means heavyweight or over 900 cc. On the other hand, “4” means under 900 cc. There can also be different numbers indicating other weight classes.
  • Characters 5 and 6 specify the model. It can be AA, AB, AC, BA, BB, BC, and so on. AA means FLH 80, and AD indicates FLH Classic. 
  • The seventh character is a letter that tells you how much power and fuel consumption you can expect from the engine. otherwise known as ‘engine displacement’. For instance, K means 1340 shovelhead, and L means 1200 Evolution Sportster. 
  • Character No. eight is a number that indicates the introduction date. “1” tells you it was a regular introduction. Meanwhile, a mid-year introduction is indicated by 2.
  • The ninth character is the check digit, which is usually a letter. It helps experts match the engine number and vehicle identification number.
  • The last character of the engine number indicates the model year. It’s a letter code that repeats every 30 years. For instance, B means 1981 or 2011, C means 1982 or 2012, etc. 

As mentioned earlier, the engine code can differ according to the year and make of the motorcycle. The arrangement of the indicators can also vary. But all HD engine numbers convey more or less this same info.

Read Also: What Are The Best And Worst Years For Harley Sportsters?

How To Verify Harley Engine Number Authenticity?

It is essential to verify the authenticity of a Harley Davidson motorcycle before you buy or sell it. 

If the number isn’t authentic, it indicates the motorcycle is stolen or modified. To avoid buying or selling such a piece, you can follow these verification methods- 

Compare with the VIN number

The engine number of your Harley Davidson is essentially an abbreviated version of the VIN number. 

So, the information provided by both should perfectly match each other. Therefore, comparing the info these numbers provide is the best way to establish authenticity. 

First, locate and decode the VIN number. Do the same for the engine number and compare the information. 

For instance, if the engine number says the motorcycle’s engine model is AD or FLH classic but the VIN tells you it’s BE or FXWG-80, then it’s a cause for concern. 

Match The Numbers on Case Halves

On most models, the manufacturer inscribes the engine number on the left and right halves of the crankcase.

Check to see if both halves are showing the same number. If they don’t, you can easily understand that something is wrong.

Read Also: What Does Red Key Light Mean On A Harley? Here Is The Answer!

Why Is The Harley Davidson Engine Number Important?

The engine number is unique for each Harley Davidson motorcycle. It is essentially the only connection left between the vehicle and its original manufacturer after it leaves the shop. 

Therefore, it is of great importance for maintenance, proof of ownership, and avoiding fraud. 

Maintenance and Performance

The maintenance schedules, fuel corrections, and other servicing needs differ across models of Harley Davidson. 

Along with the owner’s manual, the engine number can be really helpful in detecting these specific requirements. 


Once you break down the code, you or an expert can correctly identify which parts work best for your engine. As a result, you can make appropriate replacements and ensure optimum performance. 

It also saves you from using mismatched parts, which can reduce the longevity of the engine.

Read Also: What Is Harley Davidson Stage 1: Everything You Need To Know

Avoid Fraud and Legal Troubles

If the engine number isn’t authentic, chances are high that your motorcycle might not be a fully original Harley Davidson. 

Or, maybe it was used to commit a crime and later modified to avoid detection by the police. 

In either case, you must not have to do anything with such a vehicle. You will lose money and also get into trouble with the law. 

Verification of the engine number before selling or buying a Harley Davidson can save you from this.

Read Also: History Of Harley Davidson – Journey To Success 


Hopefully, you are more knowledgeable about the engine number of your Harley Davidson after this discussion. Have some more queries? Feel free to ask here. 

What Happens If The Harley Engine Number Is Missing Or Illegible?

If you aren’t driving a Harley bike that’s over 70 years old, a missing or illegible engine number is a serious problem. It will be difficult to service and repair the vehicle. There’s also a lot of risk of legal trouble. 

Can You Change The Engine Number On A Harley Motorcycle?

Tampering with the engine number on a Harley motorcycle is illegal. If you must do it, you should contact your local transportation authorities and the manufacturer. 

Can I Use The Engine Number To Check The History Of My Harley-Davidson Motorcycle?

Decoding the engine number reveals the site and year of manufacture of the motorcycle. If you want more historical data, contact the manufacturer via their official site and give them the number. Since it’s unique, they can track it all the way back and give you more specific info. 


The Harley Davidson engine number can save you from dealing with a tampered or unoriginal motorcycle. 

Plus, you will be able to ensure that your bike gets the service and repairs it deserves. 

Needless to say, it will also make you feel more confident when you work with Harley Davidson experts.

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