There was no frame identification for purpose of ownership on 1957-1969 model Sportsters.
However, there were stampings on the different parts of the frame combined with certain features that can be used to date the frame.
Click Here to view Ironhead Frame Identification in the Sportsterpedia.

The only numbers for the purpose of identification were on the engine case.

• The engine serial number is stamped on the left side of the engine case between the two cylinders.
  The first 5 or 6 digits represent the year and model ¹⁾
  From 1962-1969, models with 4 digit production (serial) numbers have an even-numbered first digit for even years and odd numbered first digit for odd years.
  

Click Here for more specific information on serial numbers and VINs in the Sportsterpedia (including the 1962-1969 Even/Odd Rule).

Engine Serial Number for 1966 Sportsters
Model Year (first 2 digits)	Model (next few digits) (up to 4)	Sequential Serial# (remaining digits)
66	XLH XLCH	(example) 12345
Example: (66XLCH 12345) indicates a 1967 XLH model and is stamped on the Left Engine Case Between the Cylinders 2)
Example Serial Number on Engine Reads: 66XLCH12345
66	XLCH	12345

• Engine type: 4 cycle Overhead Valves, 45 degree V2 ³⁾
• Displacement: 54 ci / 883 cc
• Hemi-spherical style heads
• Bore: 3 in / 7.62 cm ⁴⁾
• Stroke: 3.8125 in / 9.68 cm ⁵⁾
• 90 Degree Valve Angle
• Horsepower: 42 @ 5,500rpm (XL) ⁶⁾

⁷⁾

• Fuel capacity: 4 gal / 15.14 l (XLCH 2.2 gal / 8.328 l)⁸⁾
• Oil Capacity: 3 qts. / 2.83 l ⁹⁾
• Transmission Capacity: 1.5 pints / .71 l ¹⁰⁾
• MPG: 50mpg (est.)

• Weight: 495 lb / 225 kg

¹¹⁾

• Constant Mesh - Foot shift
• Speeds - 4 Forward
• Number of Sprocket Teeth
  • Engine: 34
  • Clutch: 59
  • Transmission: 21 (XLCH 20)
  • Rear Wheel: 51
• Gear Ratios (XL,XLH)
  • 1st: 10.63 to 1
  • 2nd: 7.69 to 1
  • 3rd: 5.82 to 1
  • 4th: 4.21 to 1
• Gear Ratios (XLCH)
  • 1st: 11.16:1
  • 2nd: 8.08:1
  • 3rd: 6.11:1
  • 4th: 4.42:1

• Tire pressure
  • Front: 14 psi / .96 bar
  • Rear: 18 psi / 1.24 bar

¹²⁾

What is the Current KBB Value? ¹³⁾

What is the Current KBB Value? ¹⁴⁾

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