X - Sportsters. These descend from the K series, 1952-56
XL- Series started in 1957. They are "unit construction" (engine & transmission share a common case).
L - High compression (7.5:1 in 1957).
H - Starting in 1958 came the XLH, meaning Higher-power or High-compression (9:1) or Hot .
C - Also in 1958 was the XLCH. The C was intended to mean "Competition".
CR- Cafe racer **, with bikini fairing.
LT- Touring, with bigger tank, thicker seat, and hard bags.
The first letter of the model designator reveals the engine series:
First character:
G - Servicar three wheeler, 1937 to 1972
E - Overhead valve 61 cubic inch "big twin" (Engine/trans separated)
F - Overhead valve 74,80 or 88 cubic inch "big twin"
FL - 80 to 88 cubic inches and a fat front tire. (Also 74" 1941-82)
K - Side valve 45 and 55 cubic inch sports bike that replaced the WL in
1953 and was replaced by the Sportster in 1957. It had many design
features that were carried over to the Sportster.
U - Side valve 74 or 80 cubic inch "big twin"
V - Side valve 74 cubic inch 1930-36. (Also 1935-36 VLH, VHS 80)
W - Side valve 45 cubic inch made 1937 to 1952
X - Sports and special construction. Applied to 1918-1922 opposed twin
Sport, 1944 military opposed twin, and 1957 to present Sportster.