How did Harley serial number their bikes? Before this, i must get you know i have searched more info on the book and hung on the web to try to find the answer, but the result is disappointing. So i turn my help for this forum. How did Harley start their serial numbers in the vintage years from the late 1950s and earlier? That is, if we took the first motorcycle off the line of a given model what would that first bike's serial number be? For example, the first knucklehead built for the 1936 model year: i.e.: 36ELxxxx would have what 4-digit number following EL? (Substitute numbers for the x's)? Hint: Most people get this wrong. Does anybody know? pls help me,thank you.