Myrons Mopeds

Table of Contents

1. P48, P3 (FBM), 2M, 3M
1. 1950’s   47.7cc     2,3-speed vert. all-iron cyl. ∅38.0

2. F48, 2M, 3M, 2B, 3B, F5
2. 1960’s   47.7cc  1,2,3-speed vert. all-iron cyl. ∅38.0

3. 3CV, 4MP, 4MP-S, 4CL-S
3. 1960’s   49.6cc     3,4-speed vert. all-iron cyl. ∅39.0  

4. Gyromat, Convert
4. 1970’s   49.0cc    1, 2-speed horiz. cylinder     ∅40.0  

4. Convert, MO, MO4
4. 1970’s   49.0cc  1,2,4-speed horiz all-iron cyl. ∅40.0  

4. MO1, MO2, MO4, Gyrokick
4. 1970’s   49.9cc  1,2,4-speed horiz all-iron cyl. ∅40.4  

5. S5K, S5K2
5. 1970’s   47.7cc    one-speed vert. all-iron cyl. ∅38.0  

5. S5R, S5E
5. 1970’s   49.55cc  one-speed vertical cylinder  ∅39.0  

6. M1, M101, M1K, MO3
6. 1980’s   49.9cc  1,2,3-speed horiz. cylinder     ∅40.4

6. M1, M1K
6. 1980’s   49.9cc    one-speed horiz all-iron cyl. ∅40.4  

7. S5N, S5T
7. 1980’s   49.55cc  one-speed vert all-alum cyl  ∅39.0  

8. M1K
8. 1990’s   49.9cc    one-speed horiz. cylinder     ∅40.4  

9. S5GS
9. 1990’s   49.55cc  one-speed vert all-alum cyl  ∅39.0  

This is only about half of all the Morini 50cc engines. 

 

 

 

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1. 1950’s 50-70cc 2, 3-speed vertical-cylinder engines

 

The first Morini and Minarelli engines in 1956-58 were mostly the same as 1954-55 Moto FBM. These 1950’s models have very rounded head fins.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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2. 1960’s 50cc 1, 2, and 3-speed vertical-cylinder engines

50’s look: The 1956-61 Franco Morini F48 1-speed looks like it’s predecessor, the 1954-55 Moto FBM P48 Pettiroso 2-speed. It has the rounded 1950’s head fins. But the F48 has no shift cable attachments and no foot shifter. That distinguishes it from the others that change gears. Otherwise it looks the same.

It is not yet known if the 1961 Morini F48 was automatic clutch or manual clutch (or both). Both types have clutch cables, and look the same on the outside. By 1968 it was automatic.

New logo: The earliest photo of the hourglass logo was this F48 from 1961.

 

Newer fins: The 1962-66 50cc motors below have the 1960’s style head fins, taller in front and less rounded (except for fan-cooled types). The shape of the cooling fins and engine case can indicate the year range. Newer fins are bigger and more square, less rounded. Newer engine cases are less rounded. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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3. 1960’s 50cc 4-speed vertical-cylinder engines

In 1964 starting with the 3CV, the bore increased from 38.0 to 39.0 mm and the stroke decreased from 42.0 to 41.5 mm. The piston and rings got bigger, but the rings also got thinner.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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4. 1970’s 50cc 1, 2-speed horizontal cylinder engines

It’s hard to find info about these. Like other Morini and Minarelli engines, the engine identity is concealed or replaced with the bike maker name. The bike maker flyers are the best source of official photos and information.

The first horizontal-cylinder Morini one-speed moped engines were not automatic. The 1968 Malaguti flyer shows this. The Dribbling model with horizontal cylinder says “monomarcia” (one speed), while the Nuovo Europino vertical cylinder model says “monomarcia a frizone automatico” (one speed automatic clutch).  

1970-type aluminum cylinder: The late 60’s and early 70’s horizontal aluminum cylinders with all-horizontal fins, have a standard bore of 40.0 mm. 

iron cylinder: These cylinders are cast iron, darker, heavier, with top and bottom fins vertical and side fins horizontal. From the front view, the fins resemble a very thick plus sign. This all-iron cylinder replaced the 1970-type iron-sleeved aluminum cylinder in the early 70’s. At first in the early 1970’s the iron cylinder had a 40.0 mm standard bore, so it would interchange with the 1970-type. Later in the mid-1970’s it had a 40.4 mm standard bore, so it would interchange with the 1977-type. But not all changed to 40.4 in the mid 70’s. Some remained 40.0 bore into the late 1970’s. Some late 1970’s owners manuals specified 40.0 mm bore: 1976 NVT Easy Rider ER1, ER2, 1977 Intramotor-Gloria Scout. Most others of this period specified 40.4 mm. 

1977-type aluminum cylinder: These were iron sleeve aluminum cylinders with bigger fins, thicker plus sign style. They were made from the early 1970’s to about 1980. Most have a 40.4 bore, but some might have been made with 40.0 bore. That is what is shown and stated in the manuals mentioned above. Maybe 1 out of 10 Morini 1977-type cylinders on US models are 40.0. About 9 out of 10 are 40.4.

 

Convert: In the mid-1970’s Morini developed a two-speed automatic version of the Gyromat, called the Convert. A Morini Convert is the precursor of the Morini MO-2.

Gyrokick: In the mid-1970’s Morini produced a kick-start version of the Gyromat, called the Gyrokick. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MO1 and MO2 Speed Versions – Differences

30mph 2.2hp 13T sprocket, 14/12 carb, Ø13 intake, same cylinder, 5mm piston skirt cut
25mph 1.4hp 12T sprocket, 14/12 carb, Ø12 intake, same cylinder, 3mm piston skirt cut
20mph 1.0hp 12T sprocket, 14/ 9  carb,  Ø9  intake, restricted cyl., 3mm piston skirt cut

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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5. 1970’s 50cc 1-speed vertical cylinder engines

S5K: The 1968? to 1972? Morini S5K had the same cast-iron cylinder and piston and head from the early 1960’s. The connecting rod had a brass bushing for the piston pin. The right-side kick start operates backward.  

 

 

 

 

 

 

 

 

 

 

 

MF logo: The above logo says MF (Morini Franco), very stylized, and very 70’s, all straight lines.

S5K2: The 1972? to 1978? Morini S5K2 has improvements over the S5K. It has a needle bearing for the piston pin, instead of a brass bushing. It has a right-side kick start lever that operates forward, with an external return spring and improved mechanism.

Manufacturers that have used this 1970’s S5 engine, or the 1980’s to late 1990’s S5 versions, are as follows: Italjet/Indian, Malaguti, LEM, KTM, Husqvarna, DBM, Young Rider plus many others.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sachs design: The S5K2 piston is an old design used by Morini and Minarelli since before their beginnings. It is 38.0mm diameter, very tall (22mm) above the wrist pin (12mm) and short below (17mm). But why are these early Italian 50cc pistons the same dimensions and design as German pistons made by Sachs?

In the early 1950’s Vittorio Minarelli visited Fichtel and Sachs in Austria to learn about moped engines. When Minarelli returned he began building engines, along with partner Franco Morini, at FBM in the 1950’s. The Italian engineers used many of German engineer Ernst Sachs production methods and knowledge, like casting and metallurgy, and design principles, like bore and stroke, port timing, sizes and thicknesses, geometry, etc.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

S5E: In the late 1970’s the S5E “Electronic” replaced the S5K2. It had an electronic ignition system instead of points ignition system. The S5E still had a cast iron piston-port cylinder, but the fins were bigger and completely square, like a 70’s Volvo! The piston changed from a 1950’s design 38mm with two thick rectangular (regular) rings, to a late-70’s 39mm with upper L-type (Dykes) ring. The crankshaft changed from 42mm stroke to 41.5, and the piston pin small brass bushing became a bigger needle bearing. Other things changed, like the forward-kick lever became aluminum. But the rest of the S5E engine and transmission remained mostly the same as S5K2. This is apparent from the illustration. 

S5R: In the late 1970’s the S5R “Radiale” was a sport version of the S5E. It had a piston-port aluminum cylinder with very big fins and a distinctive radial-fin head.  The exhaust header pipe passed through the right side engine fins. It had a bigger carburetor and intake manifold than the S5E. Serious power for an 8-year-old, without any gear shifting!

 

 

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6. 1980’s 50cc 1, 2-speed horizontal cylinder engines

M1: In 1979 Morini came out with the M1 engine, a one-speed with a case-type reed valve. The reed valve induction produced about 20-30% more torque. The result was acceleration about the same as a MO-2 two-speed, but at a much lower cost and complexity. So by about 1980, both the MO-1 and MO-2 were discontinued in favor of the M1.

 

 

 

 

M101: In 1981 the two-speed M101 came out, a variator-transmission belt-drive engine with a M1 top-end (cylinder, piston and head). The variable-ratio-pulley transmission resulted in increased acceleration over the fixed-ratio M1. The price increased and so did the weight and case length.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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7. 1980’s 50cc 1-speed vertical cylinder engines

 

 

 

 

 

 

 

 

S5N: In the early 1980’s the S5N replaced the S5E. The S5N had an aluminum piston-port cylinder, lighter in color but with the same fins. The piston design changed from L-type upper ring to both rectangular thin 39 x 1.0. The thin rings made better compression at high rpm.

S5T: In the mid 1980’s the S5T replaced the S5N. The S5T had a reed valve in the cylinder, and much bigger cooling fins. With the reed valve the intake air mixture can flow through a window in the back side of the piston, and the cylinder can have additional transfer ports on the intake side. Those benefits outweigh the extra restriction of the reed valve.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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8. 1990’s 50cc 1-speed horizontal cylinder engines

The Morini M1 was still in production in the 1990’s

 

 

 

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9. 1990’s 50cc 1-speed vertical cylinder engines

S5GS: In the early 1990’s the S5GS replaced the S5T. It had larger cooling fins, larger carburetor, and a bigger reed valve with more reed petals, 4-reed instead of 2-reed.

Manufacturers which have used this engine include: Husqvarna, KTM (pre 2001), LEM, Rivara and DBM. The Husqvarna version of this engine was fitted with an O-ring head gasket & thicker base gasket in later years.

 

 

 

 

 

 

 

 

 

 

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