Finding Your Bike's Build Date

Ever wonder when your engine was built?  Not just the model year but its actual birthday?  Well here's how to figure it out...

First, locate the crankcase number (not the same as the VIN).  On a Big Twin the number is located on the left engine case in front of and slightly below the nose of the primary case.  On a Sporty, the numbers tended to move a little from year to year, but most are stamped on the right crankcae just in front of the oil pump.

Its a 10 digit series and will begin with a 15 on 49 state Big Twins and a 20 on California Big Twins.  On Sportsters, the numbers are a bit more involved.  A 24 is an 883, 25 is a 1200, 26 is a California 883, 27 is a California 1200, 29 is a Swiss 883, 30 is a Swiss 1200, 31 an International 883, and a 32 is an International 1200.  Phew!!

The next 2 numbers are the model year.

The next 3 numbers are the day the engine was built, but they require a little decoding, a calculator and maybe even a calendar for it to be something understandable.  For example say you've got a '97 model and the 3 numbers are 090.  Get this your engine was built on March 31!!  Here's how you get there...The month of January had 31 days, February had 28 (if it were a leap year it would've had 29) and March had 31 as well.  If you add the days up for those 3 months they total 90.  This means the engine was built on March 31!!  If the number was 115, your engine was born on April 25, etc. etc.  Pretty cool huh?

Now for the last three numbers.  These numbers will tell you what number in the production line your engine was in.  For example, if the last 3 numbers on your engine were 015...your engine was the 15th engine built that day.

Anyway that's how you break down the engine numbers.

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"RJL" 8/07