V5A1M is a Vespa engine prefix/VIN code.

V5A1M is engine VIN number for 50cc engine used in 50n, 50n, 50l, 50l, 50r vespa models made through years 1963 - 1971.
P.S. This engine VIN number is for the engine block/casing and it doesn't mean that over the years and even accross the models there isn't slight modifications of this engine parts, their sizes or even internals.

V5A1M engine specification

50n (1963 - 1971) V5A1M engine specs

ENGINE: 2-stroke, 49.77 cc, Engine Code V5A1M (from 1965 was expanded to cover the hole on the cylinder housing) Bore: 38.4 mm. STROKE: 43 mm. POWER: 1.45 hp at 4500 rpm SAFC: 7,2:1 TRANSMISSION: 3 Speed, 3 clutch friction plates (from 2 to 1965, the cruise lines cruise is replaced with 4 arms) POWER: the crankcase via rotary valve driven by a crankshaft web, Dell'Orto carburetor 14 into the underseat storage with air filter, 2% mixture. WHEELS: 2 and 3/4 × 9 SUSPENSION: hydraulic shock absorber with rubber elements on the front, coil spring and hydraulic shock absorber on the rear. BRAKES: Front and rear drum. ELECTRICAL: AC 6v - 20w, HT coil Internal. LIGHT FRONT: Lighthouse diameter 105, 2 6v lamps - 15W REAR LIGHT: 6v - 5W + reflector (since 1965 are fitted with a plastic transparent red light) COLORS: 1963 - Green (Code Max Meyer 1.298.6301) 1964/65 - Amethyst Grey (1.298.8710) - Red (1.298.5847) - Green (1.298.6301) 1966 onwards - Light Blue by V5A1T 92877 onwards (1.298.7400) - Red V5A1T from 92877 to 200000 (1.298.5850) - Light Green V5A1T from 140366 to 200000 (1.298.6303) - Green Apple by V5A1T 200,001 onwards (1.298.6302) - Blue Aquamarine from V5A1T 200,001 onwards (1.298.7305) - Turquoise V5A1T from 200,001 onwards (1.298.7240) - Yellow Positano from 200,001 onwards (1.298.2902) - Moonlight Metallic (2.268.0108) RUST: Grey (Max Meyer Code 8012M) COLOR STEERING, HUB, COVER, WHEEL RIMS: Aluminum (1.268.0983) with the exception of the models in the Green 63-64 (1.298.6301) TANK: 5.2 liters including reserve. SPEED ': 40 Km / h

50l (1966 - 1970) V5A1M engine specs

engine: single cylinder, air cooled 2-stroke induction: disc valve bore: 38.4 mm stroke: 43 mm cubic capacity: 49.77 cc compression ratio: 9: 1 bhp at rpm: 2.6 @5800 lubrication: 2% oil transmission: 3 speed constant mesh 1st gear: 1: 25.12 2nd gear: 1: 14.13 3rd gear: 1: 8.94 clutch: wet - multiplate carburetor: Dell'Orto main jet: slow running jet: diffuser: main air bleed: starter jet: ignition: contact breaker & coil ignition timing: 19 degrees BTDC breaker gap: 0.3 - 0.5 mm voltage: 6 volt wheels: 9" tires: 2.75 x 9

50r (1969 - 1971) V5A1M engine specs

50n	1963-1971	50n
50l	1966-1970	50l
50r	1969-1971	50r