Myrons Mopeds

For models with engines 4M, 4MS, and 4M65

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mobylette Mopeds (Motobecane or Motoconfort)

After World War Two, many airports, rail roads, roads, power plants, pipelines, refineries and factories of Europe were damaged from bombs. So travel was mostly limited to bicycles. A bicycle was light enough to carry across a stream, or over a pile of rocks. But there was a need for long distance mobility, so the motorized bicycle (moped), originally the first motorcycles of the 1890’s-1900’s, was re-born in Europe after WWII. The first Mobylette (little mobility) was the French-made 1949 Motobecane AV3.  

1949-51 AV3   Mobylette
bicycle style tube frame and fork, 600x50B tires (20″ rims)
one speed motor

1951-54 AV31  Mobylette
bicycle style tube frame and fork, 600x50B tires (20″ rims)
one speed motor

1952-54 AV32  Mobylette
bicycle style tube frame and fork, 600x50B tires (20″ rims)
one speed motor

1955-56 AV37   Mobylette Mobymatic Luxe
bicycle style tube frame, telescoping fork, 600x50B (20″ rims)
AV35 automatic clutch motor,

1955-56 AV36  Mobylette Mobymatic Standard
bicycle style tube frame, telescoping fork, 600x50B (20″ rims)
AV35 automatic clutch motor,

1955-56 AV33  Mobylette Super Standard
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
one speed motor

1955-56 AV32M Mobylette Utilitaire
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
one speed motor

1955-56 AV32S  Mobylette Service
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
AV7 S motor

1955-56 AV31  Mobylette Luxe
bicycle style tube frame, telescoping fork, 600x50B (20″ rims)
one speed motor

 

1956-57 AV79B Mobylette
“70” sheet frame w/tank
telescopic fork, 23 x 2 (19″ rims)
variator motor
early USA model ?

Floyd Clymer would later go on to produce automotive service manuals, familiar to most home mechanics. Here he is before that, when he was editor of Cycle magazine, in Jan 1956 walking his dog with a Mobylette. Mr. Clymer was so impressed with his French freedom, that he wrote this Mobylette Report, to inform American motorcyclists. 

 

1956-57 AU78   Mobylette Superluxe
“70” sheet frame w/tank, telescopic fork, 23 x 2 (19″ rims)
variator motor
1956-57 AU75   Mobylette Monoluxe
“70” sheet frame w/tank, telescopic fork, 23 x 2 (19″ rims)
one speed motor
1957-58 AU47   Mobylette Mobymatic Standard
bicycle style tube frame, telescoping fork, 600x50B (20″ rims)
variator motor dual auto clutch (Dimoby)
1957-58 AU34   Mobylette Grand Luxe
bicycle style tube frame, telescoping fork, 600x50B (20″ rims)
one speed motor
1957-58 AU54   Mobylette Super Telescopique
bicycle style tube frame, telescoping fork, 600x50B (20″ rims)
one speed motor
1957-58 AU33  Mobylette Super Standard
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
one speed motor
1957-58 AU32M Mobylette Utilitaire
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
one speed motor
1957-58 AU32S Mobylette Service
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
AV7 S motor
1957-58 AU51   Mobylette Utilitaire Telescopique
bicycle style tube frame, telescoping fork, 600x50B (20″ rims)
one speed motor

 

1959 AV33   Mobylette Super Standard
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
one speed dual auto clutch (Dimoby)
1959 AV54   Mobylette Super Telescopique
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
one speed dual auto clutch (Dimoby)
1959 BG     Mobylette Courroie-Galet
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
AV7 Dbg motor, friction drive
1959 AV32M Mobylette Utilitaire
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
one speed motor
1959 AV32S Mobylette Service
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
AV7 S motor
1959 AV51 Mobylette Utilitaire Telescopique
bicycle style tube frame, telescoping fork, 600x50B (20″ rims)
one speed motor

 

1960 AV32S Mobylette Service
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
AV7 S motor
1960 AV32E Mobylette Service Dimoby
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
AV7 D motor
1960 BG     Mobylette Courroie-Galet
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
AV7 Dbg motor,  friction drive
1960 AV44 Mobylette Standard Telescopique
“early 40″ sheet frame, telescopic fork, 23 x 2 tires (19” rims)
AV7 Dbe motor

 

 

 

1961 AV32S Mobylette Service
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
AV7 S motor
1961 BG43   Mobylette Courroie-Galet
sheet frame, rear tank, bicycle fork, 23 x 2 tires (19″ rims)
AV7 Dbg motor,  friction drive
1961 BG43T Mobylette Courroie-Galet
sheet frame, rear tank, telescopic fork, 23 x 2 tires (19″ rims)
AV7 Dbg motor,  friction drive
1961 AV43   Mobylette Standard
sheet frame, rear tank, bicycle fork, 23 x 2 tires (19″ rims)
AV7 Db motor
1961 AV43T Mobylette Standard
sheet frame, rear tank, bicycle fork, 23 x 2 tires (19″ rims)
AV7 Db motor
1961 AV44   Mobylette Standard Telescopique
sheet frame, rear tank, telescopic fork, 23 x 2 tires (19″ rims)
AV7 Dbe motor
1961 AV44T Mobylette Standard Telescopique
sheet frame, rear tank, telescopic fork, 23 x 2 tires (19″ rims)
AV7 Dbe motor, with leg shield

 

 

1962-65 AU32S Mobylette Service
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
AV7 S motor
1962-63 CG43   Mobylette Courroie-Galet
sheet frame, rear tank, bicycle fork, 23 x 2 tires (19″ rims)
AV7 Dbg motor, friction drive, with leg shield
1962-63 AU41   Mobylette Utilitaire
sheet frame, rear tank, bicycle fork, 23 x 2 tires (19″ rims)
AV7 Sb motor
1962-65 AU42   Mobylette Utilitaire Dimoby
sheet frame, rear tank, bicycle fork, 23 x 2 tires (19″ rims)
AV7 Db motor
1962-63 AU43   Mobylette Standard
sheet frame, rear tank, bicycle fork, 23 x 2 tires (19″ rims)
AV7 Db motor

1962-65 AU44 Mobylette Standard Telescopique
sheet frame, rear tank, telescopic fork, 22 or 23 (18 or 19″ rims)
AV7 Dbe motor
1962-65 AU48 Mobylette Motomatic Standard
sheet frame, rear tank, telescopic fork, 22 or 23 (18 or 19″ rims)
AV7 Vb motor

1964-65 AV32S Mobylette Service
bicycle style tube frame, bicycle fork, 600x50B tires (20″ rims)
AV7 S motor
1964-65 BG44   Mobylette Courroie-Galet
sheet frame, rear tank, bicycle fork, 23 x 2 tires (19″ rims)
AV7 Dbg motor, friction drive, with leg shield
1964-67 AV42   Mobylette Utilitaire Dimoby
sheet frame, rear tank, bicycle fork, 23 x 2 tires (19″ rims)
AV7 Db motor

1964-65 AV44   Mobylette Standard Telescopique
sheet frame, rear tank, telescopic fork, 22 or 23 (18 or 19″ rims)
AV7 Dbe motor
1964-65 AV48   Mobylette Motomatic Standard
sheet frame, rear tank, telescopic fork, 22 or 23 (18 or 19″ rims)
AV7 Vb motor
1964-66 AV76   Mobylette Mono Standard
sheet frame with gas tank, telescopic fork, 23 x 2 tires (19″ rims)
AV7 De motor
1965-66 AV79   Mobylette Mobymatic Super
sheet frame with gas tank, telescopic fork, 23 x 2 tires (19″ rims)
AV7 V motor
1964-65 AV65   Mobylette Mono Luxe
sheet frame-tank-storage, telescopic fork, 2.25 – 18 (18″ rims)
AV7 De motor
1965-66 AV68  Mobylette Mobymatic Luxe
sheet frame-tank-storage, telescopic fork, 2.25 – 18 (18″ rims)
AV7 V motor
1964-68 AV85   Mobylette Mono Grand Luxe
sheet frame-tank-storage, telescopic fork, 2.25 – 18 (18″ rims)
AV7 De motor
1964-68 AV88   Mobylette Mobymatic Grand Luxe
sheet frame-tank-storage, telescopic fork, 2.25 – 18 (18″ rims)
AV7 V2 motor
1964-68 AV89   Mobylette Grand Touring
sheet frame-tank-storage, telescopic fork, 2.25 – 18 (18″ rims)
AV7 V2.5 motor, enclosed motor chain
1962-64 Speciale 50, SPR
sheet frame w/storage, TOP TANK, telescopic, 23 x 2 (19″ rims)
AV7 V2.5 motor, enclosed motor chain (SPR)
1965-66 SP50
sheet frame w/storage, TOP TANK, telescopic, 23 x 2 (19″ rims)
AV7 V2.5 motor

 

 

 

 

 

 

1966-68 C1 Cady
Cady sheet frame, bicycle fork, 23 x 2 tires (19″ rims)
one speed dual auto clutch (Dimoby)

1968-70 M1 Cady
Cady sheet frame, bicycle fork, 21 x 2 tires (17″ rims)
one speed dual auto clutch (Dimoby)

1971-73 M3 Cady
Cady sheet frame, bicycle fork, 21 x 2 tires (17″ rims)
one speed dual auto clutch (Dimoby)

1970-71 40   Mobylette
“40” frame, step-thru, bicycle fork, 21 x 2 tires (17″ rims)
1970’s, 1-speed Dimoby, AR2-10-707 carb, 14101 float
1968-70 AU42   Mobylette Utilitaire Dimoby
“early 40” sheet frame, bicycle fork, 23 x 2 tires (19″ rims)
AV7 Db motor
1967-70 AU46  Mobylette Mono Super Standard
“40” frame, step-thru, telescopic fork, 21 x 2 tires (17″ rims)
1970’s, 1-speed Dimoby, AR2-10-707 carb, 14101 float
1968-70 AU49  Mobylette Mobymatic Super Standard
“70” frame, step-thru, telescopic fork, 21 x 2 tires (17″ rims)
1970’s motor, 1-speed Dimoby, AR2-10-707 carb, 14101 float
1968-71 AU85  Mobylette Mono Grand Luxe
“40” frame, step-thru,, telescopic fork, 2.25 – 18 (18″ rims)
1970’s, 1-speed Dimoby, AR2-10-707 carb, 14101 float
(1970’s motor with 60’s head mount, 60’s round exhaust)

1969-71 AU88  Mobylette Mobymatic Grand Luxe
“70” frame, step-thru,, telescopic fork, 2.25 – 18 (18″ rims)
1970’s, variator Dimoby, AR2-12-707 carb, 14101 float
1969-71 AU89  Mobylette Mobymatic Grand Touring
“70” frame, step-thru, telescopic fork, 2.25 – 18 (18″ rims)
1970’s, variator Dimoby, enclosed chain, long seat
1970-71 AU56  Mobylette Mono Super Confort
“50” frame, step-thru, telescopic fork, 2.25 – 17 (17″ rims)
1970’s motor, variator Dimoby, AR2-12-705 carb, 14101 float
1970-71 AU59  Mobylette Mobymatic Super Confort
“50” frame, step-thru, telescopic fork, 2.25 – 17 (17″ rims)
1970’s motor, variator Dimoby, AR2-12-705 carb, 14101 float

 

After 1970, the AV42, 46 and 49 became the 40, 40T and 40V.

After 1970-71, the AV56 and AV59 became the 50S and 50V.

 

 

 

 

 

 

 

 

1971-74 Mobylette 40T, 40L  (was AV46)
“40” frame, step-thru, telescopic fork, 2 – 17 tires (17″ rims)
1970’s motor, 1-speed Dimoby, AR2-12-705 carb, 14101 float
1971-74 Mobylette 40V (was AV49)
“40” frame, step-thru, telescopic fork, 2 – 17 tires (17″ rims)
1970’s motor, variator Dimoby, AR2-12-705 carb, 14101 float 

1971-74 Mobylette 50S, 50L (was AV56)
“50” frame, step-thru, telescopic fork, 2.25 – 17 (17″ rims)
1970’s motor, 1-speed Dimoby, AR2-12-705 carb, 14101 float
1971-74 Mobylette 50V (was AV59)
“50” frame, step-thru, telescopic fork, 2.25 – 17 (17″ rims)
1970’s motor, variator Dimoby, AR2-12-705 carb, 14101 float

1972-73 Mobylette 85
“70” frame, step-thru, telescopic fork, 2.25 – 18 (18″ rims)
1970’s, 1-speed Dimoby, AR2-10-707 carb, 14101 float
(1970’s motor with 60’s head mount, 60’s round exhaust)
1972-73 Mobylette 88
“70” frame, step-thru, telescopic fork, 2.25 – 18 (18″ rims)
1970’s, variator Dimoby, AR2-12-705 carb, 14101 float
(1970’s motor with 60’s head mount, 60’s round exhaust)
11972-74 Mobylette 92
“90” frame, step-thru, telescopic fork, 2.25 – 18 (18″ rims)
“90” motor, variator Dimoby, AR2-13-739, 14101 float
1971-73 Mobylette 93 electronique
“90” frame, TOP TANK, telescopic fork, 2.50 – 17 (17″ rims)
“90” motor, dual variator, AR2-13-726 carb, 14101 float
1971-73 Mobylette 93D electronique 
“90” frame, TOP TANK, telescopic fork, 2.50 – 17 (17″ rims)
“90” motor, dual variator, AR2-13-726 carb, 14101 float
1972-74 Mobylette 94TT electronique
“70” frame, TOP TANK, telescopic fork, 2.50 – 17 (17″ rims)
“90” motor, dual variator, AR2-13-712 carb, 14101 float

 

 

 

 

These are the Motobecane (AV) or Motoconfort (AU) Mobylette engine models and the bike models they came on. US bike models are red. Not included here are the alias brands Wards Riverside, Raleigh, Suvega engines with their models and MB equivalents. 

 approx.  engine  xxx   bike model xxxx Gurtner    comp
xyears     model xxxx models xxxxxxx carburetor  ratio   drive

1949-51 AV3 xxxxxx AV3 Mobylette x   A10-512   6.5  Standard clutchless
1952-56 AV3.5 S xx  AV or AU 31,33     000-516   6.5  Standard clutchless
1952-59 AV7 S xxxx AV or AU 32 xxx   B10–516   6.5  Standard clutchless
1956-59 AV7 Sb xxx AV or AU 41 xxx   B10–516   6.5  Standard clutchless

1952-56 AV3.5  xxx  AV or AU 31,33    0000-516   6.5   single automatic clutch
1957-66 AV7 De xxx AV/AU 85-65-76 BA10-540   7.5  Dimoby dual auto clutch
1966-69 AV7 De xxx AV/AU 85-65-76 BA10-610   7.5  Dimoby dual auto clutch
1965-66 AV7 Db xxx AV or AU 42 xxx BA10-540   6.5  Dimoby dual auto clutch
1966-69 AV7 Db xxx AV or AU 42 xxx BA10-610   6.5  Dimoby dual auto clutch
1960-61 AV7 Dbe X  AV or AU 43,44 xBA10-540   7.5  Dimoby dual auto clutch
1966-68 AV7 Dbe X  AV or AU 43,44 xBA10-610   7.5  Dimoby dual auto clutch
1958-60 AV7 Dbg xx BG or CG 43,44 AR8.7-525   6.5  Dimoby friction drive
1967-70 M1 Isodyne X1,Cady M1,C1 AR110-674   8.0  Dimoby dual auto clutch
1970-72 M1 Isodyne Cady M1,M1PR  AR110-691   8.0  Dimoby dual auto clutch
1973-75 M3 Isodyne Cady M3PR x  AR111.5-753   8.0  Dimoby dual auto clutch
1978-79 AV7 7 xxxx  7, 7 Ranger xx  AR112-884   7.8  Dimoby dual auto clutch
1978-79 AV7 7  xxx  Model 7 30mph AR112–884   7.8  Dimoby dual auto clutch
1978-79 AV7 7?xxx  Model 7 20+25  AR110-919   6.5  Dimoby dual auto clutch
1968-77 AV7 Dc 0xx 40, 50 25+30   AR212-705   7.8  Dimoby dual auto clutch
1974-80 AV7 Dc xxx 40, 50 25+30   AR212-729   7.8  Dimoby dual auto clutch
1974-80 AV7 Dc xxx 40, 50 20mph   AR210-910   6.5  Dimoby dual auto clutch
1978-79 AV10 xxxxx 41TS, 51S, 51T  AD13-976  0.0   Dimoby, case reed valve

1958-59 AV7 V xxxx  AV or AU 68-79  BA10-549   7.5  Variator + dual auto clutch
1959-70 AV7 V2 xxx  AV or AU 88  xx AR13-488   7.5  Variator + dual auto clutch
1968-77 AV7 Vb xxx  AV or AU 48  xx BA10-549   7.5  Variator + dual auto clutch
1966-71 AV7 V2.5 x  AV89, SP50  xx-   H13-569   9.0  Variator + dual auto clutch
1966-68 AV7 V2.5 S  SP50R xxxxxxx    H13-569   9.0  Variator + dual auto clutch
1966-71 AV7 V2.5 B  AV98 xxxxxxxx    H14-626   9.0  Variator + dual auto clutch
1968-71 AV7 Vb  xxx 40V, 50V xxx   AR212–705   7.5  Variator + dual auto clutch
1972-77 AV7 Vb  xxx 40V, 50V xxx   AR212–729   7.5  Variator + dual auto clutch
1974-75 AV7 Vb  xxx 50V 25 & 30    AR212–705   7.5  Variator + dual auto clutch
1976-77 AV7 Vc  xxx 50V 25 & 30    AR212–705   7.8  Variator + dual auto clutch
1977-80 AV7 Vc  xxx 50V 30 mph    AR212–873   7.8  Variator + dual auto clutch
1977-80 AV7 Vc  xxx 50V 25 mph    AR210–737   7.8  Variator + dual auto clutch
1977-77 AV7 Z  xxxx 99Z   xx x xx    AD13–858  0.0   Variator, supercharger piston
1978-79 AV10   xxx   92GT,51V,51SU AD13-976  0.0   Variator, case reed valve
1982-83 AV10   MBK M16, 41V, 51V   AD13-971 -976 -138 Var, case reed valve
1984-98 AV10   MBK 51V, many others AD13-976  0.0 Variator, case reed valve

Sources:
1. AV7 Engines Chart from Mobylette Repair Manual, official, but only goes up to 1969.
2. motobec.fr for their awesome library of sales brochures for each year, and parts manuals
3. Dating Your Motobecane from Ets Mauger for their excellent grid of years and models
4. Motobecane Club of France for illustrations and information
5. mobyjoost on The Mobylette/Motobecane Forum UK, a Mobylette expert and enthusiast
6. La bleue pour les bleus, on Le Monde en Bleue, another Moby expert
7. Mobylette Mopeds – Owners Workshop Manual by Haynes, covers 1965-76 UK models

 

AV3 Motobecane had been making motorcycles since 1922, but after WWII they switched to making motorized bicycles. Europe’s roads were bombed out, gas stations were gone, bridges were gone, so people had to walk or climb across streams and canyons carrying their bicycles and cargo. In 1949 a lightweight moped was born out of the ashes, called Mobylette (little mobility). It’s 50cc two-stroke engine had an aluminum cylinder with a steel sleeve. It had no crank seals. Both transfers were on the right side, and the piston had transfer windows and a ridge across the top. It was not at all symmetrical left to right. That is why the exhaust exits to the left.

 

AV3.5 This also had the early scavenging design (how to get the intake in and exhaust out in one piston stroke, without mixing or wasting any). Both transfer ports were on the right side. Improvements were 1) it had a hard aluminum cylinder with a hard chrome lining, 2) it had crank seals, 3) some models had a new automatic running clutch and automatic starting clutch. It was simply called “embrayage automatique”, not “Dimoby”. But it was the first Dimoby. Once the rear wheel was moving over 5 mph, the automatic starting clutch starts the engine. Once the engine rpms get above about 2000, the automatic running clutch begins to propel the bike forward.

 

AV7 S, AV7 De  The AV7 S and AV7 De (both 1.5 hp) had a improved, completely different scavenging design, known as Schurle Loop. Intake from the crankcase was forced upward around the left and right sides of the piston. Two streams were directed towards the intake side by the left and right transfer ports. They then merged and looped around, past the spark plug, towards the exhaust side, forcing out any exhaust gases. This was more efficient. In the 1950’s all two-stroke engines adopted this design. The piston changed to a flat-dome top, but the cylinder remained all aluminum with hard chrome lined cylinder wall.

The AV7 De exhaust had a new design, called blunderbuss. Inverting the expansion chamber made the exhaust short, allowing the engine to swing, while still allowing the exhaust to expand. The new compact exhaust design allowed a new swinging engine mount design. The AV7 De V-belt was held at a constant tension automatically by a spring, instead of bolted solid and adjusted periodically. 

 

AV7 V The AV7 V (1.5 hp) had a variator, which is a belt drive with one or both pulleys that vary in size. The belt is a V-belt that grips from the sides of the V. It sinks down deeper between the V-shaped sides of the pulley, as they move apart, and raises up higher between the V-shaped sides as they come together. A set of 4 or 6 steel balls roll outward when the engine rpms increase. That forces the pulley sides together, causing the V-belt to ride higher. The result is the engine rpm stays the same as the bike accelerates.

The blunderbuss short exhaust allowed the engine to swing about 20 degrees. Below 15mph the engine is forward, in low gear, and above 25mph it is rearward, in high gear. Amazing!

 

AV7 V2, AV7 Dbe The AV7 V2 (2.0 hp) and AV7 Dbe (1.5 hp) are 95% the same as the preceding AV7 V and Db. Only the crankshaft, crank bearings, and piston changed. The old crank axles were 15mm everywhere, and took standard bearings 6302 (15 x 42 x 13) MB#00518. But installing the press-fit bearings meant dragging the clutch side bearing over the clutch clip groove and needle bearing surface, sometimes getting stuck or causing harm. The new crank was thicker at the bearings, 16mm. The bearings no longer damaged the crank during installation, but were not standard. They were special 6302-QR (16 x 42 x 13 with rounded inner edge) MB#16906. The AV7 V2 illustration does not show the 15-to-16 step in the crankshaft, because it is the older AV7 V illustration, but it does show the new crank and bearing part numbers. 

The piston design did not change. But the piston was offered in many slightly different sizes or “sorts”. The AV7 V parts diagram said 14820 for the piston, but the AV7 V2 said nothing. That is very subtle. There was a separate sheet for pistons with over ten different part numbers and sizes. Because not all of the plated cylinders are made to the exact same diameter, before this you had to sand the piston if it happened to be too tight for that cylinder, or settle for a loose fit like a worn engine has, if it happened to be too loose. 

 

 

AV7 V2.5 This was a late-1960’s 2.5 horsepower version, instead of 2.0 or 1.5 hp. It had noticeably different head fins that run at an angle instead of straight back. Both the cylinder and head fins were wider.

 

 

 

 

M1, M3 These late-60’s and early-70’s moped engines had the Dimoby dual clutch with drive belt, and magneto behind it, both on the left side. They were called Isodyne engines, which roughly means “same side”. Wierd, like Solex!

 

 

 

 

 

AV7 Vb, AV7 Dc These 1970’s models most notable differences are the square shape of the cylinder and head cooling fins (instead of round) and the all-chrome exhaust (instead of painted rear section). Many things became square in the 70’s.

AV7 Vc This was the late-70’s AV7 (2.0 or 1.5 hp) on US-models 50V series.

 

 

 

AV7 Z This 1977-only engine was a unique design. On top it has big fins and a piston-controlled reed valve. So the piston has an intake window. But look under the crankcase and you will see a second cylinder and piston. It pressurizes and depressurizes the crankcase every revolution. It is timed to be lowest pressure during the intake process, and highest during the transfer process. It is a supercharger for a two-stroke engine. But the production did not last long.

 

 

AV10 In 1978 Motobecane came out with an improved and  modernized engine design. Case reed induction is where the carburetor feeds the crankcase through a reed valve, instead of the back of the cylinder and under the moving piston. This changed the back-and-forth flow of piston-port induction to a unidirectional stop-and-go flow. The result was better performance, like 20% more low-rpm torque.

In 1981 Motobecane became bankrupt. For 2 years nothing was produced. Then they were bought by Yamaha, and their name changed to MBK. Production resumed in 1982.

By the mid-80’s pedals were no longer mandatory in most countries. So many of the mid-80’s MBK mopeds have kick-start with foot-pegs instead of pedals

 

 

 

 

Identification

Parts that are different for each version are listed here.
10 versions have 10 quantity columns. The quantity is 
0 if the part is never on that version.
1 if the part is always on that version.
1 if the part is sometimes on that version.

  E N G I N E   V E R S I O N S   
01010 12345 67890   Engines ’74-75 6 volt
52341 00010 00000 engine #4 variator 25 mph
01010 12345 67890   Engines ’76-77 6 volt       
53444 10000 00000 engine #1 Dimoby 20 mph
53949 01000 00000 engine #2 Dimoby 25 mph
53744 00100 00000 engine #3 Dimoby 30 mph
52341 00010 00000 engine #4 variator 25 mph
53745 00001 00000 engine #5 variator 30 mph
01010 12345 67890   Engines ’78-80 12 volt   
54146 00000 10000 engine #6 Dimoby 20 mph
54147 00000 01000 engine #7 Dimoby 25 mph
54149 00000 00100 engine #8 Dimoby 30 mph
54148 00000 00010 engine #9 variator 25 mph
54844 00000 00001 engine #0 variator 30 mph
01010 12345 67890    Cylinders     
22335 00100 00000 cyl. says 581051, FB2 47
23460 00001 01111 cyl. says 682051, most say nothing
53505 10000 10000 cyl. says 681051, TUM207
54328 01010 00000 cyl.   S25682051, TUM207
01010 12345 67890   Exhausts     
21103 11100 00000 exhaust  
22872 11111 11111 exhaust
01010 12345 67890   Intakes   
16673 00010 00010 intake center ∅16 x 10
16619 00001 00000 intake center ∅17 x 12 to 3/77
21201 01100 01100 intake side    ∅19 x 12
22899 00001 00001 intake side    ∅19 x 13? 3/77 on
53496 10000 10000 intake side    ∅19 x 10
01010 12345 67890   Intake Gaskets   
52646 10000 10000 intake gasket round hole
17073 01111 01111 intake gasket rectangle hole
01010 12345 67890   Carburetors 
20026 00001 00000 carb AR2-12-705 center ∅17
22160 01100 00000 carb AR2-12-729 side-5 ∅19
22160 00000 01100 carb AR2-12-729 side-6 ∅19
52175 00010 00000 carb AR2-10-737 center ∅16
52175 00010 00000 carb AR2-10-759 center ∅16
52175 00000 00010 carb AR2-10-991 center ∅16
54115 10000 00000 carb AR2-10-910 side-5 ∅19
54115 00000 10000 carb AR2-10-910 side-6 ∅19
54973 00001 00000 carb AR2-12-873 side-5 ∅19
54973 00000 00001 carb AR2-12-873 side-6 ∅19
54973 00000 00001 carb AR2-12-978 side-6 ∅19
01010 12345 67890 Model 50, 50V Chains
18368 10000 10000 chain   99L+1 for 12 x 48T
17693 01000 01000 chain   96L+1 for 11 x 44T
18427 00100 00100 chain   97L+1 for 13 x 44T
17785 00011 00011 chain 102L+1 for 11 x 54T
01010 12345 67890 Model 40 Chains
18429 10000 10000 chain   93L+1 for 12 x 48T
20766 01000 01000 chain   90L+1 for 11 x 44T
53874 00100 00100 chain   91L+1 for 13 x 44T

 

 

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Sources

1977 Motobecane America Dealer Manual
’76-’77 40TS, 40TL, 50S, 50L engines 1, 2, 3
’76-’77 50VL 0000, 0000, 00  engines 4, 5
’76-’77 Solex 4600

 

1978 Motobecane America Dealer Manual
’76-’77 40TS, 40TL, 50S, 50L engines 1, 2, 3
’76-’77 50VL 0000, 0000, 00  engines 4, 5
’76-’77 Solex 4600

 

 

1979 Motobecane America Dealer Manual
’78-’80 40T, 50S, 50L, Traveler  engines 6, 7, 8
’78-80 50VL, 50VLA, 50VLS xx  engines 9, 0
’78-80 50VLX, Moby, Le Moped engines 9, 0
’78-80 Model 7, Sebring, Solex 4600

 

 

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Discussion

Porting: The deepest secret is that there are four different cylinders, all identical on the outside. The different cylinders could have different port widths and heights (duration’s). Much more needs to be learned and explained. Why does a 2 hp one-speed model have a different cylinder than a 2 hp variable speed model?   

Gearing: The drive belt is the same for all versions. The 1-speed front pulley is the same for all versions. The 2-speed front pulley is the same for all versions. The rear pulley (without the front sprocket) is the same for all versions. Therefore, the pulley ratio is the same for all versions. The variator models in “low gear” have the same pulley ratio as the Dimoby models. As the rear wheel speed increases, the variator makes the front pulley bigger. The engine swings back as the front pulley grows, until it is in “high gear”. In high gear the pulley is about 40% bigger. So even though the variator models are geared low (small front and large rear) in chain sprockets, the variator makes up for it, above 18mph, by making the overall gearing about the same. 

 

1974-1981 Motobecane (USA models)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1980 Family Photo: Above are all of the 1980 Motobecane USA models and colors, from the sales brochure. The Sebring is made in Italy and is covered in a separate section, under Italy-made/MB Sebring. The Solex is made in France but covered in a separate section, under France-made/Solex.

Center Stands:  Notice how the center stands on the Moby and Traveler are more vertical than most Motobecane center stands. That is because these photos are of brand new bikes. The center stands become angled more forward with age or heavy use. 

Speed Version is on ID plate: On the frame behind the headlight is the ID plate. The lower squares say model (left) and speed version (right), stamped in. Before 1980, A=30, B=25, C=20. From 1980 on, A=20, B=25, C=30. Before 1978, no letter, just 20, 25, or 30 (mph). Hope yours is a 30! 1980 was the last year for US models. 1981 had new 17 digit VIN and new EPA and DOT noise and safety regulations. That  was “the last straw”. 

Contents:   1. 1982-84 Trac   M56 engine, pedal start Clipper, Eagle, Hawk, Magura controls

Contents:   2. 1984-86 Trac   M56 engine, pedal start Clipper, Eagle, Hawk, Domino controls

Contents:   3. 1986-90 Trac DP50 engine, pedal start Clipper, Olympic, Sprint or Hawk, Blitz

Contents:   4. 1984-90 Trac DM50 engine,   kick start Escot, Liberty, Liberty LS, Image, Metro

 

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1. 1982-84 with M56 engine

 

1982-84 Trac mopeds are made in Korea by Kia Motorcycle Company, Ltd. The engine, made in Korea by Daelim Motor Co. (DMC), is a remake of a 1978-80 Laura M56 engine originally made in Holland and used on Batavus mopeds.

Some of the components are European, and some are Korean. This matters for parts compatibility. The spoke wheels, brakes, speedometer, shocks, forks, fenders and seat are Korean or Asian. European things are CEV (Italian) lights and switches, Bosch (German) magneto, Magura (German) controls, Grimeca (Italian) mag wheels, Encarwi (Dutch) carburetor, and the Laura (Dutch) M56 remake engine and exhaust.

  seat: xx solo xxXx  solo xXxx   solo xxXxx   long  xXxx   long xxXxx   long  xXxx  long
wheels: spoke xXx  mags xXx   spoke xXxx   mags  xXx   spoke xxxx   mags  xXx  spoke

1982   Clipper   Eagle I dlx   Eagle I std   Eagle II dlx   Eagle II std   Hawk dlx   Hawk std

1983   Clipper   Eagle I dlx   Eagle I std   Eagle II dlx   Eagle II std   Hawk dlx   Hawk std

1984   Clipper   Eagle I dlx   Eagle I std   Eagle II dlx   Eagle II std   Hawk dlx   Hawk std

In Trac parts manuals “standard” or “deluxe” refers to the wheels, on Eagle and Hawk.

In Trac parts manuals “I” or “II” refers to the seat, solo or long, on Eagle. Most are Eagle II (long seat).

 

Hawk weight 120 lbs

 

 

 

 

 

 

Eagle weight 100 lbs

in-frame gas tank 1.2 gal

 

 

 

 

 

 

Clipper weight 115 lbs

rear gas tank 1.0 gal

 

 

 

 

 

 

 

All models: Laura M56 engine, Daelim re-make

The original Dutch-made Laura M56 engine was on 1978-80 Batavus Regency and Regency HS. 

 

 

 

 

 

 

 

 

 

 

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2. 1984-1986 with M56 engine

1984-86 Trac mopeds are mostly the same as 1982-84, except for:

1) the controls are 1980’s Domino black, instead of 1970’s Magura silver

2) the cables are different for the Domino controls

3) the switches are integrated instead of separate clamp-on.

4) the wiring is different for the new integrated (built-in) switches

 

 

 

 

 

 

  seat: xx solo xxXx  solo xXxx   solo xxXxx   long  xXxx   long xxXxx   long  xXxx  long
wheels: spoke xXx  mags xXx   spoke xXxx   mags  xXx   spoke xxxx   mags  xXx  spoke

1984   Clipper   Eagle I dlx   Eagle I std   Eagle II dlx   Eagle II std   Hawk dlx   Hawk std

1985   Clipper   Eagle I dlx   Eagle I std   Eagle II dlx   Eagle II std   Hawk dlx   Hawk std

1986   Clipper   Eagle I dlx   Eagle I std   Eagle II dlx   Eagle II std   Hawk dlx   Hawk std

 

 

 

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3. 1986-1990 with DP50 engine

Since 1984 Trac made the Escot and Image “no-peds” with the Daelim DM50 2-speed automatic engine. It was proven to be good. In 1986 Trac introduced a pedal version Daelim DP50 1-speed automatic for their models Clipper and Hawk. Both DM50 and DP50 had oil injection, where you don’t have to mix oil with the gas. The older M56 engine models needed 50:1 premix oil and gas.

The DP50 engine replaced the 1982-86 Laura M56 Daelim remake engine. During 1986 both engine types were sold, as not all models and colors changed at once. 

In late 1986 or early 1987, the Hawk was renamed Sprint.

 

 

 

 

 

 

 

 

 

 

In 1986 the Olympic, and kick version Liberty, replaced the Eagle. The Olympic was all Korean or Asian made. So most of the parts are different from the other models. The brakes were bigger, and the fork improved, true hydraulic with oil dampening, for a smoother ride.

 

 

 

 

 

 

 

 

 

 

DP50 upgrades: In 1987 two things were improved.

1) The change lever E13-9 was upgraded to a cable-less type. The start cable and start lever below the left handlebar were eliminated.

More on this later …

2) The gear set E7B-3 and E8B-13 was upgraded. Gear E7B-3 has a rounded square center hole. The four engage balls move inward (to disengage the motor for easy pedaling) and outward (to engage the motor) into the four corners of the square hole. These gears crack at one of the corners, when the engage process is not done gently. The upgraded gear set has 3? more teeth on the E7B-3 gear and 3 less on the mate gear E8B-13. More teeth made the E7B-3 gear thicker at the four corners where it was cracking at.

Driveshaft gear E7B-3 changed from #13009 (24T) to #18750 (27T?).

Idleshaft gear E8B-13 changed from #13019 (23T) to #18751 (20T?).

More on this later …

 

 

In 1988 the Blitz came out. It was an Olympic with a solo seat and luggage rack. 

  seat: xx solo xxx  long xx   long  xxx  solo
wheels: spoke xx spoke x    mags  xx spoke

1986   Clipper    Olympic     Hawk

1987   Clipper    Olympic     Sprint

1988   Clipper    Olympic     Sprint  x Blitz

1989   Clipper    Olympic     Sprint  x Blitz

 

 

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4. 1984-1990 with DM50 engine

 

 

 

 

 

 

 

 

 

  seat: xx solo xx  solo xx   long  xxx  solo
wheels: spoke x spoke x    mags  xx spoke

1984 x  Escot  x Liberty xx Image

1985 x  Escot  x Liberty xx Image

1986 x  Escot  x Liberty xx Image x Liberty LS

1987 x  Escot  x Liberty xx Image x Liberty LS

1988 x  Escot  x Liberty xx Image x Liberty LS

1989 x  Escot  x Liberty xx Image  xx Metro

 

 

 

 

 

 

 

 

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1987-1990 Trac DH100