Pistons and Rings

July 13, 2014

Contents:    1. Rings    2. Ring Info    3. Pistons     4. Piston Info

 


1. Piston Rings for Sale

Ring Types: Most vintage mopeds have rectangular cross section rings, where both the top and bottom are flat. Most Asian two-stroke rings have a trapezoidal cross section, where the top slants downward as you go inward. Some vintage mopeds have a Dykes or “L” type upper ring, at the very top of the piston.

FG gap style (aka GN)

Key:    R = rectangular     T = trapezoidal     L = L-ring (Dykes)

ring size is the cylinder size that the ring would have a 0.004 to 0.008″ gap in.
height is the thickness up-and-down. T & L rings have 2 heights, outer & inner.
width is the depth inward-and-out. L rings have two widths, outer and inner.

FG (foro grano) = ring pin is on side of groove = GN (grano normal)
GI (grano interno) = pin is in center of groove

n.a. = none available      Prices are for each ring, unless noted.


part #   style  size x height x width  gap  price  applications                   35 to 44 cc


2229812 xx R 36.50 x 1.50x x.xx xx   FG  $10 Tomos MC36 36cc


part #   style  size x height x width  gap  price  applications                  45 to 49 cc

SachsD xx R 38.00 x 1.50x x.xx xx   GI  $10 Sachs 1979-later 504, 505 1C,1D (upper only)
233707 xx T 38.00 x 1.5/1.3 x 1.60  FG  $17 Tomos A55 (2001-06) superceeded to rectangular
236802 xx R 38.00 x 1.50x x.xx xx   FG  $10 Tomos A35 (1991-06), A55 (2007-on)
Derbi xxxx R 38.00 x 1.50x x.xx xx   FG  $10 Derbi 1976-1985 (lower only), Odyssey, SoloSolo)
DerbiL xxx L 38.00 x 2.0/1.0 x 1.5/0.5   $10 Derbi 1976-1985 (upper ring) fits Puch loose inner
PuchL xxxxL 38.00 x 2.0/1.0 x 1.7/0.7   n.a. Puch 1979-1980 deluxe models upper
203300 xx R 38.00 x 2.00x x.xx xx   FG  $10 Puch (except hi-torque late with L-ring upper)
Sachs xxxx R38.00 x 2.00x x.xx xx   FG  $10 Sachs 504, 505 1A,1B (both) 1C,1D (lower only)
044754 xx 3R8.00 x 2.00x x.xx xx   FG $ 10  Tomos A3 1975-1990, Morini S5K2, others
Allstate xx R 38.00 x 2.50x x.xx xx   FG  $20/2 Minarelli V1 1hp 20mph, Sears Allstate, early Puch
Solex45 x  R 38.00 x 2.50x x.xx xx  flat  n.a. Solex 45cc 1946-1954
182518 xx R 38.20 x 1.50x x.xx xx   FG  $10 Vespa 79-later & some 78s lower ring
166945 xx R 38.20 x 2.00x x.xx xx   FG  $20 Vespa 78-80 USA-type, must file down a 077775
182519  xx L 38.20 x 2.0/1.0 x 1.8/.75    $15 Vespa 79-later & some 78s upper ring
132515  xx R 38.40 x 1.50x x.xx xx   FG  $15 1st oversize lower ring, for Vespa 79-later & some 78s
3010010 x T 38.40 x 1.5/1.3 x x.xx  FG  n.a. Kinetic TFR (Vespa Si remake) 95-later
077775 xx R 38.40 x 2.00x x.xx xx   FG  $12 Vespa 77-earlier & some 78s, early Kinetic
G.68473 x L 38.40 x 2.0/1.0 x 1.8/.75    n.a 1st oversize upper ring, for Vespa 79-later & some 78s
227758 xx R 38.50 x 1.50x x.xx xx   FG  $12 1st oversize for Tomos A35
044751 xx R 38.50 x 2.00x x.xx xx   FG  $10 1st oversize for Tomos A3
98196 xxx R 38.60 x 2.00x x.xx xx   FG  $15 1st oversize for Sachs 504, 505, 2nd oversize Vespa 79- lower
4635 xxxx R 38.70 x 1.50x x.xx xx   FG  $18 Minarelli V1 1.5, 2hp 25, 30mph (after 1979)
DemmUxx L 38.80 x 2.0/1.0 x 1.65/0.6  $30 Demm Smily upper
4640xxxxx R 38.80 x 1.50x x.xx xx   FG  $10 Minarelli V1 1.5, 2hp 25, 30mph (until 1979)
DemmLxxxR 38.80 x 2.00x x.xx xx   FG  n.a. Demm Smily lower
710095 xx L 39.00 x 2.0/1.0 x 1.65/0.6  $25 Morini S5R, S5T, S5E, S5ET kids off road, upper
710159 xx R 39.00 x 1.00x x.xx xx   GI  $20 for some LEM dirt bikes Morini #261060
4650 xxxx R 39.00 x 1.50x x.xx xx   FG  $25 1st oversize for Minarelli V1 1.5, 2hp 25, 30mph
261044 xx3 R9.00 x 1.50x x.xx xx   FG  $25  Morini S5R, S5T, S5E, S5ET kids off road, lower
22148 xxx R 39.00 x 2.00x x.xx xx   GI  $12 Motobecane (GI after June 1976)
14821 xxx R 39.00 x 2.00x x.xx xx   FG n.a. Motobecane (FG before July 1975)
Diblasi xx   39.00 x 2.00x x.xx xx   FG  $15  DiBlasi folding mini-cycle
281220 xx R 39.03 x 2.00x x.xx xx   GI  $14 Jawa 207 1970-83 standard
4660 xxxx R 39.20 x 1.50x x.xx xx   FG  $17 2nd oversize for Minarelli V1 1.5, 2hp 25, 30mph
2812201 x R 39.28 x 2.00 x 1.65 xx GI  $18 1st oversize for Jawa 207
4670 xxxx R 39.40 x 1.50x x.xx xx   FG  $17 3rd oversize for Minarelli V1 1.5, 2hp 25, 30mph
HDM50 xx R 39.40 x 1.50x x.xx xx   GI  n.a. Aermacchi Harley Davidson M50 std 1966-67
Solex xxxx R 39.50 x 1.70 x 1.60 xxflat  n.a. Solex rings (3) no locating pins
2812202 x R 39.53 x 2.00 x 1.65 xx GI  $20 Jawa 2nd oversize
4680 xxxx R 39.60 x 1.50x x.xx xx   FG  $17 4th oversize for Minarelli V1 1.5, 2hp 25, 30mph
4690 xxxx R 39.80 x 1.50x x.xx xx   FG  $17 5th oversize for Minarelli V1 1.5, 2hp 25, 30mph
633086 xx T 40.00 x 1.2/1.0 x 1.60  FG  $30/2 China 49cc two-strokes most
PGOup xx  T 40.00 x 1.2/1.0 x 1.70  GI  $17 PGO Star 50 upper, other Asian 49cc
PGOlow xx R 40.00 x 1.20 x 1.85 xx GI  $15 PGO Star 50 lower, others
Honda xxx T 40.00 x 1.5/1.3 x 1.80  FG  n.a. Dailim Trac both, upper Honda NC50,PA50
Honda xxx T 40.00 x 1.5/1.3 x 1.80 FG  n.a.  upper ring for Yamaha QT50, others
551916 xx R 40.00 x 1.50 x x.xx xx  FG  $10 Batavus M48, M56, Trac
Honda xx r 4 0.00 x 1.50 x x.xx xx  FG $ 15  lower for Honda NC50,PA50, Yamaha QT50
Benelli xx R40.00 x 1.50 x x.xx xx  FG $1 5  Benelli G2 moped, 1966 Wards Riverside 450SS moped
Benelli xx R40.00 x 1.50 x x.xx xx  FG $1 5  Benelli Fireball and other 1965-75 mini cycles 50cc
551913 xx R 40.00 x 1.50 x x.xx xx  GI  $15 Verona (like Morini MO-1 but 40mm not 40.4)
Kreidler xxR 40.00 x 1.50 x x.xx xx  GI  $15 Derbi 1986-1989 flat reed, Kreidler Flory
30702100  R 40.00 x 2.00 x x.xx xx  FG  $12 Casal, Garelli, Avanti (most), Hero Majestic
Peugeot xx R 40.00 x 2.50 x x.xx xx  GI  $20 Peugeot 102, 103 (almost all US models)
30802700 R  40.20 x 2.00 x x.xx xx  FG  $15 1st oversize for Garelli
633087 xx R 40.25 x 1.00 x x.xx xx  FG  $25/2 1st oversize for China 49cc two-strokes
Honda xxx T 40.25 x 1.5/1.3 x 1.80  FG  n.a. 1st oversize for Honda NC50,PA50 upper
480511 xx R 40.25 x 1.50 x x.xx xx FG  $15 1os for Batavus, 1os for Honda NC50,PA50 lower
4641b xxx R 40.30 x 1.50 x x.xx xx FG  $20 Minarelli V1HL and V1L lower, filed down 40.5
4641a xxx L 40.30 x 2.0/1.0 x 1.8/0.7   n.a. Minarelli V1L, upper
551905 xx R 40.40 x 2.00 x x.xx xx FG  $12 2os for Garelli, Dailim DP50,DK50
30802800  R 40.40 x 2.00 x x.xx xx FG  $15 2nd oversize for Garelli, original
261045 xx R 40.40 x 1.50 x x.xx xx GI  $20/2 Morini MO1, MO2, M1 engines
Honda xxx T 40.50 x 1.5/1.3 x 1.80  FG  n.a. 2nd oversize for Honda NC50,PA50 upper
632758 xx R 40.50 x 1.50 x x.xx xx FG  $12 2os for Batavus, 2os for Honda NC50,PA50 lower,
PeugOS xx R 40.50 x 2.50 x x.xx xx GI  $12 some Peugeot 102, 103, but none in California
261046/6  R 40.60 x 1.50 x x.xx xx GI  n.a. 1st oversize for Morini MO1, MO2, M1 engines
4651b xxx  R 40.60 x 1.50 x x.xx xx FG  $10 1st oversize for Minarelli V1L lower
30802900  R 40.60 x 2.00 x x.xx xx FG  $10 3rd oversize for Garelli
4651a xxx L 40.60 x 2.0/1.0 x 1.8/0.7   $15 1st oversize for Minarelli V1L upper
Honda xxx T 40.75 x 1.5/1.3 x 1.80  FG  n.a. 3os Honda NC50,PA50 upper, #130A4-GA6-003
Honda xxx R 40.75 x 1.50 x x.xx xx FG  n.a. 3os Honda NC50,PA50 lower, #130A4-GA6-003
261046/8  R 40.80 x 1.50 x x.xx xx GI  $12 2nd oversize for Morini MO1, MO2, M1 engines
40.8ring x R 40.80 x 1.50 x x.xx xx FG  $12 oversize for Laura or others
30803000  R 40.80 x 2.00 x x.xx xxFG  $10 4th oversize for Garelli
Gyro xxxx R 41.00 x 1.20 x x.xx xx  GI  n.a. Honda Gyro std rings #13010-GJ5-015 =set
632795  x T 41.00 x 1.5/1.3 x 1.80  GI  $15 Suzuki FY50,FZ50,FA50


part #   style  size x height x width  gap  price  applications                        50 to 54 cc


41.6ring x R 41.60 x 1.50 x x.xx xx GI  $15 for something Italian

 

 


2. Piston Ring Information

Pinned or Not Pinned: Most moped piston rings are two-stroke style, where there are pins in the ring grooves of the piston that keep the rings from rotating around. Two stroke cylinders have holes or ports that the ring ends can snag on. So two stroke rings are pinned to the piston. Four stroke cylinders do not have any holes, so four stroke rings are not pinned. Knowing about those pins is important when installing.    

Getting the right rings: If your model is not in the applications, then you must measure the bore and the ring thickness. A calipers is the best tool to measure the bore (ring diameter) and ring thickness. Sometimes your rings might not be original, for many reasons. The piston might be aftermarket with thinner rings. The cylinder might be bored out to an oversize bore. Some mopeds came with more than one piston size or ring style.

Break a ring, how not to: Two stroke pistons have little pins (stumps, bumps) in the piston ring grooves that prevent the rings from rotating. Knowing where each ring locating pin is, and aligning the ring gap over the pin during cylinder installation, is the key to not breaking the ring. 

Measuring wear: A new piston ring is a the best tool to measure how worn a cylinder is. Conversely, a new cylinder is the best tool to measure how worn a ring is. To measure the wear of a ring, you need a perfectly round cylinder of a precisely known bore. A worn cylinder that has not been honed will still have it’s original new bore at the very top, above where the rings rub at. A new ring in a new cylinder should have a very small end gap of .004 to .008″. A worn but still OK cylinder with a new ring will have a gap of .0010 to .018″. A worn cylinder and ring both will have an end gap of over .020″(.5mm). A badly worn cylinder and/or ring will have a huge gap, over .030″(.75mm). You measure ring gap with a feeler gauge.

Classifying Jawa Rings

Classifying Piston Rings

Classifying rings: Rings get mixed up and are difficult to tell the size, unless a perfectly round cylinder of an appropriate size is available to place the ring in. If you try to squeeze a piston ring into a circle with just fingers, it inevitably becomes a very rounded polygon, or at best an ellipse. So the measurement becomes inaccurate. At right is how Myrons Mopeds’s Jawa piston rings were classified, using a piece of aluminum tubing with a tight fitting piston inside it to hold the tube round, and the test ring square. From top to bottom, 39.03 x 2.0, 39.28 x 2.0, 39.53 x 2.0, 39.78 x 2.0mm. Each ring increases in diameter by 0.25mm, so the circumference increases by Pi times that, or about 0.8mm. Here the inside of an old fishing pole tube is 39.78mm, perfect for the 3rd oversize 39.78 ring, on the bottom, with a gap of almost zero. Each gap is 0.8mm more because each ring is 0.25mm less diameter. It is important that the piston and ring fit the cylinder properly.   

Filing down: To make a ring slightly smaller, one of the two ring ends can be filed down, while preserving the shape. To reduce the size (diameter) by 0.20 mm, the end must be filed down by pi times that, 0.63 mm. When a filed down ring is installed in a cylinder smaller than it was designed for, two things change. The tension is greater, and the shape is slightly non-circular. So filed rings need a longer break-in period, to wear down the higher places. With 38 to 41 mm rings, the size can be reduced by 0.2mm with about 30 minutes of break-in, and by 0.5mm with about 2 hours of break-in. After break-in the rings have a mirror polish all around.

Why is the width not specified? Because the inner side of the ring does not touch anything. The ring has spring tension pushing it outwards, keeping the bottom (inner) surface from touching the bottom of the ring groove. So the ring width can be any amount, from about half the groove depth, to the groove depth. The exact ring width is not important. Exact ring height and diameter are important. 

 

 


3. Pistons for Sale

Moped pistons are listed by pin size,
then upper size, then diameter.

3a. Moped Pistons with 10mm Pins
18mm upper: 70’s-80’s Tomos (A3), 50’s-60’s Puch and Tomos
19mm upper: Solo (Odyssey, Columbia), TYM (Angel)
20mm upper: Honda NC50, PA50, Yamaha QT50, PW50
21mm upper: 1990’s Vespa, 2000’s China 49cc two-stroke 

3b. Moped Pistons with 12mm Pins
16mm upper: Peugeot 102, 103, Morini MO1, MO2, M1, M101
17mm upper: 1969-on Puch, 1991-on Tomos, ’75-86 Derbi
18mm upper: Garelli, Laura (Batavus, Trac), ’87-89 Derbi
19mm upper: 1970’s Kreidler Flory, 1990’s Honda NSR50
20mm upper: 1970’s-80’s Piaggio (Vespa), 1990’s Kinetic
21mm upper: 1980’s Minarelli V1L, V1HL, Suzuki FA50
22mm upper: 1970’s Minarelli V1, Sachs 504, 505, Morini S5
23mm upper: 1970’s Casal, Zundapp?

3c. Moped Pistons with 13mm Pins
15.5mm upper: 1970’s Motobecane

3d. Moped Pistons with 14mm Pins
18mm upper: 1970’s Jawa

 

Install pistons with arrow towards exhaust, or else ring ends can snag on ports.
Piston actual diameter is measured at skirt (bottom), where it is largest.
All new pistons come with new rings, clips, pin
 
Abbreviations:  “size” = cylinder bore                1.2-0F = trapezoidal (slanted) ring 1.2 x 1.0mm, FG gap style
FG (foro grano) = side pin ring gap style               1.5-3G = trapezoidal (slanted) ring 1.5 x 1.3mm, GI gap style
GI (grano interno) = center pin gap style               Dykes = “L” type ring, usually on upper
 

3a. Pistons with 10mm Wrist Pins 

 

Part      “size” pin upper lower diam  ring1   ring2   piston  price   18mm T A L L (Pin to Crown)
number         mm  mm  mm  mm   specs   specs  maker            Tomos A3, 1950’s – 60’s Puch & Tomos
=============================================================================
??????    38.00  10 18.0 24.0 37.94  2.0FG   2.0FG  Mahle     n.a.  Tomos A3 20mph 1.0hp (55 total, 52 at edge)
??????    38.00  10 18.0 21.0 37.94  2.0FG   2.0FG  Mahle     n.a.  Tomos A3 25mph 1.5hp (52 total, 49 at edge)
207403   38.00  10 18.0 19.0 37.94  2.0FG   2.0FG  Mahle    $50   Tomos A3 30mph 2.0hp (50 total, 47 at edge)
Vertex    38.00  10 18.0 19.0 37.95  1.5FG   1.5FG  generic  $60   aftermarket Tomos A3 (50 total, 47 at edge)
206200   38.00  10 18.0 18.0 37.9x  2.0FG   2.0FG  generic   n.a.  aftermarket Tomos A3 (49 total, 46 at edge)
202420   38.50  10 18.0 19.0 38.45  2.0FG   2.0FG  Mahle    $75   Tomos oversize A3 30mph 2hp
 
Tomos A3 piston

18mm upper, 10 pin,  Tomos A3 1974-91

18mm upper, 10 pin, 1950s-60's Puch

18mm upper, 10mm pin,  1950’s-60’s Puch

Solo Piston

Solo Piston

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Part          “size” pin upper lower diam  ring1   ring2   piston  price   19mm T A L L (Pin to Crown)
number             mm  mm  mm  mm   specs   specs  maker            Solo (Odyssey and Columbia), Angel (TYM)
=============================================================================
2200593  38.00  10 19.0 22.0 37.9x  1.5FG  1.5FG  Mahle    n.a.   Solo piston “N”
2200600  38.00  10 19.0 22.0 37.9x  1.5FG  1.5FG  Mahle    n.a.   Solo piston “U”
xxxxxxxx  40.00  10 19.0 15.0 39.92  1.5FG  1.5FG  xxxxxx    n.a.   Angel/Speed Bird
 
 
 Angel and Batavus pistons
 
A Batavus piston (12 x 33 mm pin) can substitute for an Angel piston (10 x 33 pin), if the piston pin needle bearing is changed. The 10x14x13 needle bearing (with 2mm rollers) needs to be 12x14x13. But there are none that thin (1mm rollers). So a bronze bushing 12x14x13 must be used instead of a needle bearing, like one from a Puch.  There are already oil holes in the Angel rod. Those holes need to extend through the bronze bushing to oil the pin.
 
 
 
 
 
 
 
Part      “size” pin upper lower diam  ring1   ring2   piston  price   20mm T A L L (Pin to Crown)
number         mm  mm  mm  mm   specs   specs  maker            Honda NC50, PA50, Yamaha QT50, PW50
=============================================================================
Honda    40.00  10 20.0 18.0 39.95  1.5-3F  1.5FG  Honda    n.a.   Honda NC50 Express and PA50 (has decomp cut)
Honda    40.00  10 20.0 18.0 39.9x  1.5-3F  1.5-3F  generic   n.a.   Honda NC50, PA50 (after cutting decomp)
Yamaha  40.00  10 20.0 17.5 39.9x  1.5-3F 1.5FG  Yamaha  n.a.  Yamaha QT50 Yamahopper and PW50
20mm upper (10mm pin) Honda NC50

20mm upper, 10mm pin,   Honda NC50, NA50, PA50

Honda NC50 and PA50 piston new

20mm upper, 10 pin Honda NC50/NA50

20mm upper (10mm pin) Yamaha QT50 & PW50

20mm tall at edge, 10mm pin,      Yamaha QT50 & PW50 (1980’s)

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Part      “size” pin upper lower diam  ring1   ring2   piston  price   21mm T A L L (Pin to Crown)
number         mm  mm  mm  mm   specs   specs  maker            Vespa (90’s Euro models), China scooters
=============================================================================
Meteor   38.20  10 21.0 17.0 38.13  1.5FG   1.5FG  Meteor   $60  Vespa Ciao & Si, 90’s Euro models w/10mm pin
??????    38.20  10 21.0 17.0 38.1x  Dykes  1.5FG  generic   n.a.   Vespa Ciao & Si, 90’s Euro models w/10mm pin
632964   40.00  10 21.0 18.0 39.9x  1.2-0F 1.2-0F  generic  $60   E-Ton 50cc 2-stroke scooter
632965   40.25  10 21.0 18.0 40.1x  1.2-0F 1.2-0F  generic  $60  oversize for E-Ton 50cc 2-stroke scooter 
 
 
21mm upper, 10 pin, Vespa Euro models

21 upper, 10 pin,
Vespa Euro models

21mm upper, 10mm pin Chinese scooters

21 upper, 10 pin Chinese scooters

 
 
 
 
 
 
 
 
 
 
 
 
 
 

3b. Pistons with 12mm Wrist Pins 

Part      “size” pin upper lower diam  ring1   ring2   piston  price   1 6 m m   T A L L   (Pin to Crown)
number         mm  mm  mm  mm   specs   specs  maker            Peugeot 103, 102  Morini MO1, MO2, M1, M101
=============================================================================
Kawasaki 39.00  12 16.0 18.0 38.95  1.2-0F 1.2-0F generic   n.a.  Kawasaki AR50 
69707     40.00  12 16.0 17.0 39.88  2.5GI   2.5GI  Peugeot  $90  Peugeot original Sort A
69708     40.00  12 16.0 17.0 39.89  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort B
69709     40.00  12 16.0 17.0 39.90  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort C
peugAA   40.00  12 16.0 17.0 39.90  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort AA(=C)
69710     40.00  12 16.0 17.0 39.91  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort D
peugBB   40.00  12 16.0 17.0 39.91  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort BB (=D)
Verona   40.00  12 16.0 17.0 39.92  1.5GI   1.5GI  Asso       n.a.  Verona (like MO1), 3mm skirt cut
Benelli   40.00  12 16.0 17.0 39.xx  1.5FG   1.5FG  Asso      n.a.  Benelli G2 (has transfer windows)
69711     40.00  12 16.0 17.0 39.92  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort E
PeugCC   40.00  12 16.0 17.0 39.92  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort CC (=E)
69712     40.00  12 16.0 17.0 39.93  2.5GI   2.5GI  Peugeot  $95  Peugeot original Sort F
MF553-F 40.00  12 16.0 17.0 39.93  1.5GI   1.5GI  generic   $90  MMI aftermarket for Peugeot
peugDD   40.00  12 16.0 17.0 39.93  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort DD (=F)
69713     40.00  12 16.0 17.0 39.94  2.5GI   2.5GI  Peugeot  $95  Peugeot original Sort G
peugEE   40.00  12 16.0 17.0 39.94  2.5GI   2.5GI  Peugeot  $95  Peugeot original Sort EE (=G)
69714     40.00  12 16.0 17.0 39.95  2.5GI   2.5GI  Peugeot  $95  Peugeot original Sort H
peugFF   40.00  12 16.0 17.0 39.95  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort FF (=H)
69715     40.00  12 16.0 17.0 39.96  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort I
peugGG   40.00  12 16.0 17.0 39.96  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort GG
peugHH   40.00  12 16.0 17.0 39.97  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort HH
peugII    40.00  12 16.0 17.0 39.98  2.5GI   2.5GI  Peugeot  n.a.  Peugeot original Sort II
MF553-C 40.00  12 16.0 17.0 39.95  1.5GI   1.5GI  generic   $90  MMI aftermarket for Peugeot
MO4       40.40  12 16.0 17.0 40.33  Dykes  1.5GI  Asso       n.a.  Mor MO2 foot shift, 3mm cut, “ASSO 1929MO4”
230125   40.40  12 16.0 17.0 40.31  1.5GI   1.5GI  generic  $70  Morini MO1,MO2, 3mm skirt cut, says nothing
230125   40.40  12 16.0 17.0 40.32  1.5GI   1.5GI  Asso       $70  Morini MO1,MO2, 3mm skirt cut, “ASSO.W 2352”
230134   40.40  12 16.0 17.0 40.32  1.5GI   1.5GI  Asso       $80  Morini M1, zero skirt cut away, “ASSO W 1929M1”
230125   40.40  12 16.0 17.0 40.32  1.5GI   1.5GI  Asso       $70  Morini MO1,MO2, 3mm skirt cut, “ASSO 1929”
230125   40.40  12 16.0 17.0 40.35  1.5GI   1.5GI  Asso       $70  Morini MO1,MO2, 5mm skirt cut, “ASSO.W 2351”
230136    40.40 12 16.0 17.0 40.3x  1.5GI   1.5GI  Asso      n.a.   Morini M101 variator engine
69716     40.50  12 16.0 17.0 40.44  2.5GI   2.5GI  Peugeot  $60  Peugeot oversize original Sort K
69717     40.50  12 16.0 17.0 40.45  2.5GI   2.5GI  Peugeot  $60  Peugeot oversize original Sort L
69718     40.50  12 16.0 17.0 40.46  2.5GI   2.5GI  Peugeot  $60  Peugeot oversize original Sort M
69719     40.50  12 16.0 17.0 40.47  2.5GI   2.5GI  Peugeot  $60  Peugeot oversize original Sort N
69720     40.50  12 16.0 17.0 40.48  2.5GI   2.5GI  Peugeot  $60  Peugeot oversize original Sort P
69721     40.50  12 16.0 17.0 40.49  2.5GI   2.5GI  Peugeot  $60  Peugeot oversize original Sort Q
230126/6 40.60 12 16.0 17.0 40.53  1.5GI   1.5GI  Asso      $80  1os Mor MO1,MO2, 3mm skirt cut, “ASSO 1929”
230135/6 40.60 12 16.0 17.0 40.5x  1.5GI   1.5GI  Asso      n.a.  1os Mor M1, zero skirt cut away, “ASSO W 1929M1”
230136/6 40.60 12 16.0 17.0 40.5x  1.5GI   1.5GI  Asso      n.a.  1os for Morini M101 variator engine
230126/8 40.80 12 16.0 17.0 40.72  1.5GI   1.5GI  Asso      $85  2os Mor MO1,MO2, 3mm skirt cut, “ASSO 1929”
230135/8 40.80 12 16.0 17.0 40.7x  1.5GI   1.5GI  Asso      n.a.  2os Mor M1, zero skirt cut away, “ASSO W 1929M1”
230136/8 40.80 12 16.0 17.0 40.7x  1.5GI   1.5GI  Asso      n.a.  2os for Morini M101 variator engine
230126/0 41.00 12 16.0 17.0 40.90  1.5GI   1.5GI  generic  $85  3os Mor MO1,MO2, 3mm skirt cut, says nothing
 
16mm upper, 12 pin, Peugeot

12 x 16 x 17, Peugeot

16mm upper height pistons Peugeot left and Morini right

12 pin, 16mm tall (pin to top edge)
#69717 Peugeot and #230125 Morini

16mm upper, 12mm pin, Morini piston #230136

12 pin x 16 upper x 17mm,
Morini M101 piston #230136

 
 
 
 
 
 
 
 
 
 
 
 
 
1995 Hero Panther

12 pin, 16 upper, 17 lower, 1995 Hero Panther

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Part     “size” pin upper lower diam  ring1   ring2   piston  price   1 7 m m   T A L L   (Pin to Crown)
number        mm  mm  mm  mm   specs   specs  maker            Puch, Tomos ’92-on, Derbi pre-’87 
=============================================================================
229803    36.50  12 17.0 18.0 36.43  1.5FG  1.5FG  Vertex  $60  Tomos MC36 36cc kids dirt bike
406300    38.00  12 17.0 19.0 37.91  2.0FG  2.0FG  generic $50  Puch early 2000’s aftermarket, way too small
406300    38.00  12 17.0 18.0 37.93  2.0FG  2.0FG  generic $50  Puch aftermarket Step II, made too small
233709    38.00  12 17.0 20.6 37.95  1.5-3F 1.5-3F Vertex  n.a.  Tomos A55 Alu cyl, pre 2007 with trap. Rings
233709    38.00  12 17.0 20.6 37.95  1.5FG  1.5FG  Vertex  n.a.  Tomos A55 Alu cyl = 37.98 “07-09 14140 37.98”
409000    38.00  12 17.0 18.0 37.95  1.5FG  1.5FG  generic n.a.  aftermarket Tomos A35
223747    38.00  12 17.0 18.0 37.95  1.5FG  1.5FG  Vertex  $70  Tomos A35 std, has windows on in side
8025090  38.00  12 17.0 23.0 37.95  Dykes  1.5FG  Mahle   n.a.  Derbi std 1976-86 says “1003 E 119 A” ?
106.9/21  38.00  12 17.0 20.5 37.95  2.0FG  2.0FG  Mahle   n.a.  Puch Alu cyl Sort 1 = 37.98 says “38 1 1019”
??????     38.00  12 17.0 20.5 37.95  2.0FG   none  Mahle   $95  Puch Alu cyl Sort C = 37.99 says “38 C 1734”
106.9/22  38.00  12 17.0 20.5 37.96  2.0FG  2.0FG  Mahle   n.a.  Puch Alu cyl Sort 2 = 37.99 says “38 2 1019”
??????     38.00  12 17.0 22.0 37.96  2.0FG  2.0FG  Mahle   n.a.  Puch H-T cyl Sort 11 38.00 says “38 1 1116”
??????     38.00  12 17.0 23.0 37.96  Dykes  2.0FG  Mahle   n.a.  Puch H-T cyl Sort 11 38.00 “38.0 11 1593a”
??????     38.00  12 17.0 22.0 37.967 2.0FG  2.0FG  Mahle   n.a.  Puch H-T cyl Sort 22 38.007 says “38 2 1116”
??????     38.00  12 17.0 23.0 37.967 Dykes  2.0FG  Mahle   n.a.  Puch H-T cyl Sort 22 38.007 “38.0 22 1593a”
106.9/23  38.00  12 17.0 20.5 37.97  2.0FG  2.0FG  Mahle   n.a.  Puch Alu cyl Sort 3 = 38.00 says “38 3 1019”
??????     38.00  12 17.0 23.0 37.974 2.0FG  2.0FG  Mahle   n.a.  Puch H-T cyl Sort 33 38.014 says “38 3 1116”
??????     38.00  12 17.0 23.0 37.974 Dykes  2.0FG  Mahle   $95  Puch H-T cyl Sort 33 38.014 “38.0 33 1593a”
106.9/24  38.00  12 17.0 20.5 37.98  2.0FG  2.0FG  Mahle   n.a.  Puch Alu cyl Sort 4 = 38.01 says “38 4 1019”
106.9/24  38.00  12 17.0 20.5 37.98  2.0FG  2.0FG  Mahle   $80  Puch Alu cyl Sort 4 = 38.01 good used
106.9/25  38.00  12 17.0 20.5 37.99  2.0FG  2.0FG  Mahle   $95  Puch Alu cyl Sort 5 = 38.02 says “38 5 1019”
8025091  38.25  12 17.0 20.0 38.14  Dykes  1.5FG  Mahle   $80  Derbi 1os 1976-86 says “1003 E 120 B 0.25”
??????     38.205 12 17.0 20.0 38.15  Dykes  1.5FG  Mahle   $80  Derbi 1os 1976-86 says “1002 E 030”
??????     38.25  12 17.0 20.0 38.16  Dykes  1.5FG  Mahle   $95  Derbi 1os 1976-86 says “1003 E 120 A 0.25”
??????     38.25  12 17.0 20.0 38.15  Dykes  Dykes  Mahle   $80  Derbi 1os 1976-86 says “Mahle 10 0.25”
??????     38.25  12 17.0 23.0 38.19  Dykes  2.0FG  Mahle   $95  Puch H-T cyl 22 oversize says “38.25 22 1593a”
??????     38.25  12 17.0 23.0 38.19  Dykes  2.0FG  Mahle   $95  Puch H-T cyl 22 oversize says “38.25 22 1593a”
8025092  38.40  12 17.0 20.0 38.3?  Dykes  1.5FG  Mahle   n.a.  2os for Derbi original 1976-1986
8025093  38.70  12 17.0 20.0 38.6x  Dykes  1.5FG  Mahle   n.a.  3os for Derbi original 1976-1986
227334    38.50  12 17.0 20.5 38.4x  1.5FG  1.5FG  Vertex  n.a.  oversize original for Tomos A35
409001    38.50  12 17.0 20.x 38.4x  1.5FG  1.5FG  generic $60  oversize aftermarket for Tomos A35
8025094  38.90  12 17.0 20.0 38.8x  Dykes  1.5FG  Mahle   n.a.  4os for Derbi original 1976-1986t

MWards  40.00  12 17.0 18.0 39.9x  1.5FG   1.5FG  Asso      n.a.  Benelli 1960’s (has transfer windows)
??????     40.00  12 17.0 19.0 39.94 1.5-3F 1.5-3F Yamaha $40  Yamaha what? new, no rings, non avail.
??????     40.25  12 17.0 19.0 40.22 1.5-3F 1.5-3F Yamaha $40  Yamaha what? new, no rings, non avail.
 
17mm upper (12 pin) Puch

17 upper, 12 pin, Puch aftermarket

17mm upper (12 pin) Derbi Variant pre-'87

17mm upper ,12 pin,   Derbi Variant pre-’87

17mm upper, 12mm pin, Tomos A35 1992-06

17 upper, 12 pin, Tomos A35 92-06

17mm upper, 12 pin, Benelli

17mm upper, 12 pin, Benelli MW and G2

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Part     “size” pin upper lower diam  ring1   ring2   piston  price   1 8 m m   T A L L   (Pin to Crown)
number        mm  mm  mm  mm   specs   specs  maker            Derbi ’87-89, Garelli, Batavus, Trac
=============================================================================
2500091  40.00  12 18.0 19.0 39.945 1.5GI  1.5GI  Mahle   n.a.  Derbi 1986-1989 flat reed eng, Sort A
2500091  40.00  12 18.0 19.0 39.95  1.5GI  1.5GI  Mahle   n.a.  Derbi 1986-1989 flat reed eng, Sort B
2500091  40.00  12 18.0 19.0 39.955 1.5GI  1.5GI  Mahle   n.a.  Derbi 1986-1989 flat reed eng, Sort C
2500091  40.00  12 18.0 19.0 39.96  1.5GI  1.5GI  Mahle   n.a.  Derbi 1986-1989 flat reed eng, Sort D
2500091  40.00  12 18.0 19.0 39.965 1.5GI  1.5GI  Mahle   n.a.  Derbi 1986-1989 flat reed eng, Sort E
50582150 40.00 12 18.0 ??.?  39.9?  2.0FG  2.0FG  Asso     n.a.  flat top, Garelli alum cylinder 20,25mph
50882150 40.00 12 18.0 ??.?  39.9?  2.0FG  2.0FG  Asso     n.a. flat top, Garelli alum cylinder 30mph
50532181 40.00 12 18.0 ??.?  39.9?  2.0FG  2.0FG  Asso     n.a.  Garelli cast iron cyl 25mph
408211    40.00 12 18.0 14.0 39.92  1.5FG  1.5FG  generic $70  Daelim (Trac) aftermarket (rect. rings)
408201    40.00 12 18.0 16.0 39.92  1.5FG  1.5FG  generic $60  Garelli/Batavus aftermarket
??????     40.00 12 18.0 14.0 39.9x  1.5-3F 1.5-3F  generic   n.a.  Daelim (Trac) original (trap. rings)
480580    40.00 12 18.0 14.0 39.95  1.5FG  1.5FG  Mahle   n.a.  Batavus M48 original says 39.95
80016     40.00  12 18.0 14.0 39.9x  1.5FG  1.5FG  Mahle   n.a.  Batavus/Trac M56 original Sort A
80017     40.00  12 18.0 14.0 39.9x  1.5FG  1.5FG  Mahle   n.a.  Batavus/Trac M56 original Sort B
80018     40.00  12 18.0 14.0 39.98  1.5FG  1.5FG  Mahle   n.a.  Batavus/Trac M56 original Sort C
80019     40.00  12 18.0 14.0 39.9x  1.5FG  1.5FG  Mahle   n.a.  Batavus/Trac M56 original Sort D
80020     40.00  12 18.0 14.0 40.0x  1.5FG  1.5FG  Mahle   n.a.  Batavus/Trac M56 original Sort E
??????     40.00  12 18.0 14.0 40.0x  1.5FG  1.5FG  Mahle   n.a.  Batavus/Trac M56 original Sort F
00012184 40.20  12 18.0 16.0 40.1x  2.0FG  2.0FG  Asso     n.a.  1os for Garelli cast iron cyl 20,30mph
50532184 40.20  12 18.0 ??.? 40.1x  2.0FG  2.0FG  Asso     n.a.  1os for Garelli cast iron cyl 25mph
480581    40.25  12 18.0 14.0 40.20  1.5FG  1.5FG  Mahle   $95  1os for Batavus, original
00012182 40.40  12 18.0 16.0 40.3x  2.0FG  2.0FG  Asso     n.a.  2os for Garelli cast iron cyl 20,30mph
50532182 40.40  12 18.0 ??.? 40.3x  2.0FG  2.0FG  Asso     n.a.  2os for Garelli cast iron cyl 25mph
534404    40.40  12 18.0 17.0 40.33  2.0FG  2.0FG  GOL     $55  2os for Garelli (made in Italy)
00012185 40.60  12 18.0 16.0 40.5x  2.0FG  2.0FG  Asso     n.a.  3os for Garelli cast iron cyl 20,30mph
50532185 40.60  12 18.0 ??.? 40.5x  2.0FG  2.0FG  Asso     n.a. 1os for Garelli cast iron cyl 25mph
00012183 40.80  12 18.0 16.0 40.7x  2.0FG  2.0FG  Asso     n.a.  4os for Garelli cast iron cyl 20,30mph
50532183 40.80  12 18.0 ??.? 40.7x  2.0FG  2.0FG  Asso     n.a.  2os for Garelli cast iron cyl 25mph
 
18mm upper, 12 pin Daelim (Trac)

18mm upper, 12 pin Daelim (Trac)

18mm upper, 12 pin, Batavus

18mm upper, 12 pin, Garelli

18mm upper, 12 pin, Garelli

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Part             “size” pin upper lower diam  ring1   ring2   piston  price   1 9 m m   T A L L   (Pin to Crown)
number                mm  mm  mm  mm   specs   specs  maker            Kreidler Flory, Honda NSR50
=============================================================================
13101-GE2-305 39.00 12 19.0 16.0 38.94 1.2-0F 1.2FG generic n.a.  Honda NS50 1990, std
13102-GE2-305 39.25 12 19.0 16.0 39.19 1.2-0F 1.2FG generic n.a.  Honda NS50 1990, 1os
13103-GE2-305 39.50 12 19.0 16.0 39.44 1.2-0F 1.2FG generic n.a.  Honda NS50 1990, 2os
13104-GE2-305 39.75 12 19.0 16.0 39.69 1.2-0F 1.2FG generic n.a.  Honda NS50 1990, 3os
2150383d        40.00 12 19.0 15.2 39.93  1.5GI  1.5GI  Mahle  $80  Kreidler Flory Sort D “Mahle R021 40154+”
2150383d        40.00 12 19.0 15.2 39.95  1.5GI  1.5GI  Mahle  $80  Kreidler Flory Sort D, cyl=39.98 “R021 40154+”
2150383f         40.00 12 19.0 15.2 39.96  1.5GI  1.5GI  Mahle  $80  Kreidler Flory Sort F, cyl =39.99 “R021 40154+”
2150383h        40.00 12 19.0 15.2 39.97  1.5GI  1.5GI  Mahle  $80  (good used)    Sort H, cyl=40.00 “R021 40154+”
2150383m        40.00 12 19.0 15.2 39.98  1.5GI  1.5GI  Mahle  $80  Kreidler Flory Sort M, cyl=40.01 “R021 40154+”
 
19mm upper, 12 pin, Kreidler

19mm upper, 12 pin, Kreidler

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Part     “size” pin upper lower diam  ring1   ring2   piston  price   2 0 m m   T A L L   (Pin to Crown)
number        mm  mm  mm  mm   specs   specs  maker            Vespa (Piaggio), Kinetic
=============================================================================
182591    38.20  12 20.0 16.0 38.12  2.0FG  2.0FG  Piaggio $60 good used, Vespa 1977-78 “USA” version
191034    38.20  12 20.0 16.0 38.1x  Dykes  1.5FG  Piaggio  n.a. Vespa 1979-later and some 1978
Kinetic    38.40  12 20.0 16.0 38.30  1.5-3F 1.5-3F  generic  n.a. Kinetic (Vespa copy), good used, no arrow
132521    38.40  12 20.0 16.0 38.32  2.0FG  2.0FG  Piaggio $50 good used, Vespa 1973-77 & some 1978
182592   38.40  12 20.0 16.0 38.32  Dykes  1.5FG  Piaggio $75 1os for Vespa 1979-later & some 78
182593   38.60  12 20.0 16.0 38.5x  Dykes  1.5FG  Piaggio  n.a. 1os or 2os for Vespa
137682   38.80  12 20.0 16.0 38.74  Dykes  1.5FG  Piaggio $65 2os or 3os for Vespa
633992    40.00  12 20.0 17.0 39.9x 1.2-0F 1.2-0F  generic $60 China 49cc two-strokes
 
Vespa pistons have skirt cut-outs rotated 30 deg                      “SC” means scoria (exhaust)
 
20mm upper, 12mm pin, Vespa

20mm upper, 12mm pin,   Vespa mopeds pre-1978     rings: both 38.4 x 2.0

20mm upper, 12 pin, Vespa L-ring

20mm upper, 12mm pin, Vespa mopeds 1979-80  rings: Dykes, 38.2 x 1.5

20mm upper, 12 pin, China two stroke

20 upper, 12 pin, China scooters, rings: 40 x 1.2 trap

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Part     “size” pin upper lower diam  ring1   ring2   piston  price   2 1 m m   T A L L   (Pin to Crown)
number        mm  mm  mm  mm   specs   specs  maker            Minarelli V1L, V1HL, Suzuki FA50
=============================================================================
4541      40.30  12 21.5 15.0 40.2x  Dykes  1.5FG  Minn.    n.a.  Minarelli V1L reed valve engine
4543      40.30  12 21.5 15.0 40.2x  Dykes  1.5FG  Minn.    n.a.  Minarelli V1HL reed valve engine for trike
4551      40.60  12 21.5 15.0 40.5x  Dykes  1.5FG  Minn.    n.a.  1os for Minarelli V1L
4553      40.60  12 21.5 15.0 40.5x  Dykes  1.5FG  Minn.    n.a.  1os for Minarelli V1HL reed w/electric start
4561      40.80  12 21.5 15.0 40.7x  Dykes  1.5FG  Minn.    n.a.  2os for Minarelli V1L
4563      40.80  12 21.5 15.0 40.7x  Dykes  1.5FG  Minn.    n.a.  2os for Minarelli V1HL
FY50     41.00  12 21.0 15.0 40.92  1.5-3G 1.3-3G Suzuki  n.a.  Suzuki FY50, FZ50, FA50 std
230140  46.00  12 21.0 17.0 45.93  Dykes  1.5GI   Asso    $70  Morini S5T big bore 39->46mm
 
21mm upper, 12 pin, Suzuki FA50

21mm upper, 12 pin, Suzuki FA50/FZ50

 
 
 
 
 
 
 
 
  
 
 
 
 
 
 
Part     “size” pin upper lower diam  ring1   ring2   piston  price   2 2 m m   T A L L   (Pin to Crown)
number        mm  mm  mm  mm   specs   specs  maker            Minarelli V1, Sachs 504, 505, Morini S5
=============================================================================
552        38.00  12 22.0 16.0 37.9x  2.0FG  2.0FG  Mahle   n.a.  0286 378-005 Sachs 504 505 1A,1B “37.98 577”
230101   38.00  12 22.0 17.0 37.9x  2.0FG  2.0FG  Asso    n.a.  Morini S5K2, can use Minarelli #4500?
406500   38.00  12 22.0 13.5 37.91  1.5FG  2.0FG  generic $55  Sachs aftermarket 504, 505 1C,1D says “38”
553        38.00  12 22.0 14.0 37.95  1.5FG  2.0FG  Mahle   n.a.  0286 378-051 Sachs 504,505 1C,1D
4500      38.00  12 22.0 16.0 37.94  2.5FG  2.5FG  Asso    n.a.  Minarelli V1 1hp 20mph
4510      38.20  12 22.0 16.0 38.1x  2.5FG  2.5FG  Asso    n.a.  1os for Minarelli V1 1hp 20mph
230102   38.20  12 22.0 17.0 38.1x  2.0FG  2.0FG  Asso    n.a.  1os for Morini S5K2, can use Minarelli #4510?
4520      38.40  12 22.0 16.0 38.3x  2.5FG  2.5FG  Asso    n.a.  2os for Minarelli V1 1hp 20mph
4530      38.60  12 22.0 16.0 38.5x  2.5FG  2.5FG  Asso    n.a.  3os for Minarelli V1 1hp 20mph
SachsO   38.60  12 22.0 16.0 38.5x  2.0FG  2.0FG  Mahle  $60  Sachs oversize original 504, 505 1A,1B
4535      38.70  12 22.0 16.0 38.64  1.5FG  1.5FG  Minn.    n.a.  Minarelli V1 1979-on 1.5,2hp (some)
4540HP   38.80  12 22.0 15.5 38.75  Dykes  2.0FG  Asso   $80  Demm Smily piston, almost Minarelli

4540      38.80  12 22.0 16.0 38.74  1.5FG  1.5FG  Minn.   $80  Minarelli V1 1.5,2hp pre-1979
4550      39.00  12 22.0 16.0 38.94  1.5FG  1.5FG  Minn.   $80  Minarelli V1 first oversize
4560      39.20  12 22.0 16.0 39.14  1.5FG  1.5FG  Minn.   n.a.  Minarelli V1 second oversize
4570      39.40  12 22.0 16.0 39.34  1.5FG  1.5FG  Minn.   $80  Minarelli V1 third oversize
4580      39.60  12 22.0 16.0 39.54  1.5FG  1.5FG  Minn.   n.a.  Minarelli V1 fourth oversize
230133A 39.00  12 22.0 16.0 38.98  1.5FG  1.5FG  Asso    n.a.  Morini S5R, S5T (alum cyl 1sp kick)
230133B 39.00  12 22.0 16.0 38.97  1.5FG  1.5FG  Asso    n.a.  Morini S5R, S5T (alum cyl 1sp kick)
230133C 39.00  12 22.0 16.0 38.96  1.5FG  1.5FG  Asso    n.a.  Morini S5R, S5T (alum cyl 1sp kick)
230133D 39.00  12 22.0 16.0 38.95  1.5FG  1.5FG  Asso    n.a.  Morini S5R, S5T (alum cyl 1sp kick)
230133E 39.00  12 22.0 16.0 38.94  1.5FG  1.5FG  Asso    n.a.  Morini S5R, S5T (alum cyl 1sp kick)
230133F 39.00  12 22.0 16.0 38.93  1.5FG  1.5FG  Asso    n.a.  Morini S5R, S5T (alum cyl 1sp kick)
4550      39.00  12 22.0 16.0 38.9x  1.5FG  1.5FG  Minn.   n.a.  1st oversize for Minarelli V1
4560      39.20  12 22.0 16.0 39.1x  1.5FG  1.5FG  Minn.   n.a.  2nd oversize for Minarelli V1
4570      39.40  12 22.0 16.0 39.3x  1.5FG  1.5FG  Minn.   n.a.  Harley Davidson M50 std, 3os for Min V1
4580      39.60  12 22.0 16.0 39.5x  1.5FG  1.5FG  Minn.   n.a.  4th oversize for Minarelli V1
4590      39.80  12 22.0 16.0 39.7x  1.5FG  1.5FG  Minn.   n.a.  5th oversize for Minarelli V1
4595      40.00  12 22.0 16.0 39.9x  1.5FG  1.5FG  Minn.   n.a.  6th oversize for Minarelli V1
Bigbore  45.40  12 22.0 18.0 45.33  1.5FG  1.5FG  Minn.    $70  Minarelli original new in box, 1.5 FG rings
Bigbore  45.40  12 22.0 18.0 45.32  1.5FG  1.5FG  Minn.    $40  Minarelli original new in box, no rings, none avail.
Morini    47.20  12 22.0 17.0 46.99  x.xXX  x.xXX  generic $70  Morini original new in box
Morini    47.15  12 22.0 17.0 47.06  x.xXX  x.xXX  generic $70  Morini original new in box
 
22mm upper, 12mm pin, Morini S5E piston 23-0133 D

22mm upper, 12mm pin,    Morini S5E #23-0133 D

16mm pin-edge to crown-edge, 12 pin, Morini S5 series (1970's -2002)

22mm upper, 12 pin, 39mm bore,    Morini  “late” S5 series (80s – 90’s)

 

 

 

 

 

 

 

 

22mm upper, 12 pin, Minarelli V1

22 upper, 12 pin, Minarelli #4540

22mm upper, 12 pin, Sachs 504/505

22 upper, 12, Sachs 504/505

 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
Part     “size” pin upper lower diam  ring1   ring2   piston  price   2 3 m m   T A L L   (Pin to Crown)
number        mm  mm  mm  mm   specs   specs  maker            Casal, Zundapp?
=============================================================================
Casal    40.00  12  23.0 16.0 39.95  2.0FG  2.0FG  Mahle  $70  Casal, Zundapp?, bottom is flat
 

3c. Pistons with 13mm Wrist Pins 

Part #  “size”  pin upper lower diam  ring1   ring2   maker   price        Applications =============================================================================
22273      39.00  13 15.5 21.5 38.92  2.0GI  2.0GI   MBK      n.a.  Motobecane Sort 2 cyl 38.95 (unmarked)
22274      39.00  13 15.5 21.5 38.93  2.0GI  2.0GI   MBK      n.a.  Motobecane Sort AA 38.96 (unmarked)
22275      39.00  13 15.5 21.5 38.94  2.0GI  2.0GI   MBK      n.a.  Motobecane Sort A cyl 38.97 (unmarked)
22276      39.00  13 15.5 21.5 38.95  2.0GI  2.0GI   MBK      n.a.  Motobecane Sort C cyl 38.98 (unmarked)
22277      39.00  13 15.5 21.5 38.96  2.0GI  2.0GI   MBK      n.a.  Motobecane Sort E cyl 38.99 (unmarked)
22278      39.00  13 15.5 21.5 38.97  2.0GI  2.0GI   MBK      n.a.  Motobecane Sort G cyl 39.00 (unmarked)
22279      39.00  13 15.5 21.5 38.98  2.0GI  2.0GI   MBK      n.a.  Motobecane Sort J cyl 39.01 (unmarked)
22280      39.00  13 15.5 21.5 38.99  2.0GI  2.0GI   MBK      n.a.  Motobecane Sort L cyl 39.02 (unmarked)
22281      39.00  13 15.5 21.5 39.00  2.0GI  2.0GI   MBK      n.a.  Motobecane Sort N cyl 39.03 (unmarked)
22435      39.00  13 15.5 21.5 39.01  2.0GI  2.0GI   MBK      n.a.  Motobecane Sort P cyl 39.04 (unmarked)
 

3d. Pistons with 14mm Wrist Pins 

Part #  “size”  pin upper lower diam  ring1   ring2   maker   price        Applications =============================================================================
281218    39.02 14 18.0 15.0 38.96  2.0GI 2.0GI  Jawa    n.a.  Jawa standard, no pin or clips
281218/1 39.27 14 18.0 15.0 39.23  2.0GI 2.0GI  Jawa   $65  Jawa 1st over, no pin or clips
281218/2 39.52 14 18.0 15.0 39.46  2.0GI 2.0GI  Jawa    n.a.  Jawa 2nd os, no pin or clips
281218/3 39.77 14 18.0 15.0 39.73  2.0GI 2.0GI  Jawa    n.a.  Jawa 3rd os, no pin or clips
281218/4 40.02 14 18.0 15.0 39.96  2.0GI 2.0GI  Jawa    n.a.  Jawa 4th os, no pin or clips
 
 

4. Piston Information

It’s important that the piston fits the cylinder properly. An old messed up piston that fits correctly is better than a new piston that fits too loose or too tight. Too loose will be hard to start and weak. Too tight will seize up when hot. Often a cylinder needs to be bored out slightly to fit an oversize piston. Some aluminum cylinders have plated walls that cannot be bored out. The piston diameter, measured at the skirt, is a hair smaller than the cylinder bore.

The following piston/cylinder clearance limits are from the Puch factory service manual:

Puch “Lo-torque” nikasil plated aluminum (7-fin) cylinders:  Min .0008“(.020mm)   Max .0016“(.040mm)

Puch “Hi-torque” steel sleeved aluminum (8-fin) cylinders:  Min .001″  (.029mm)    Max .002“(.055mm)

 Puch  “Magnum” steel sleeved aluminum (9-fin) cylinders:  Min .001″  (.029mm)    Max .002“(.055mm)

As the engine gets hot, the piston to cylinder clearance approaches zero. Besides “diam“, “upper“, “pin“, and “lower“, other things matter in piston compatibility. The ring pins must locate the ring gaps so they never pass over a port. The exhaust-side skirt must be long enough to cover the exhaust port at tdc. The intake-side skirt, on a piston port two stroke, controls the intake timing. Shorter skirt opens sooner and closes later. A longer intake skirt is one way some mopeds are restricted in power. Simply grind the excessively long piston skirt back to 30mph specification, but no farther, to de-restrict the piston. Puch, Tomos, Garelli are the main kinds that use longer pistons to lower the speed, for 25 and 20mph states or jurisdictions.  This list contains all pistons made by original equipment manufacturers, although most of them are no longer available. The not-available ones are listed for their information, such as speed versions or piston size choices. If you happen to have an unknown piston with or without a part number, you can identify what it is from this list by measuring it and looking for matching measurements. From all these specifications, perhaps a compatible piston can be found or adapted. 

 

Jawa USAJawa Pistons  ==========================

Jawa pistons can have 15 possible sizes:
28-1218/0 Standard…….. A Y . B Y . C Y
28-1218/1 First oversize 1A Y 1B Y 1C Y
28-1218/2 Second over.. 2A Y 2B Y 2C Y
28-1218/3 Third over….. 3A Y 3B Y 3C Y
28-1218/4 Fourth over.. 4A X 4B X 4C X

Jawa pistons have 14mm piston pins, thicker than any other 50cc piston. There is not a good substitute for Jawa piston, not even one with a smaller pin. For a 12 pin, the upper distance of 18 would need to become 19. The only piston that Myrons knows of, available, with a 12 pin and 19 upper, is for a Honda NS50, but that piston has a big intake window for a reed valve. The window would have to be somehow blocked off. Kreidler pistons would substitute, but they are all 40mm and unavailable. For a 13 pin the upper distance of 18 would need to become 18.5. The only 13 pin piston is way too short at 15.5.

Jawa Pistons

Markings: The marking on top can tell the size. Decode the marking using the left caption. Then look up the size of the piston or cylinder using the right table. 

 For example, this “1B Y” piston is supposed to measure 39.21 mm. The measurement is “34,5mm from the base” which is just below the lower ring. Four pistons actually measured 39.21 there, and 39.23 at the skirt. Other “1B” pistons were 39.20 and 39.22, 39.21 and 39.22, The rest were “B” (standard) 38.94 and 38.96, “2B” 39.44 and 39.46, “3B” 39.70 and 39.73, “4B” two at 39.95 and 39.97. Based on these eleven new pistons, all measured the same way at the same time, the Jawa piston sizes can be translated to standard piston sizes. The Jawa sizes (at the lower ring) are, on average, 0.02 mm less than standard sizes (at the skirt).

From the Puch service manual (at top of this page), the piston to cylinder clearance for a similar steel sleeved aluminum cylinder, is minimum 0.030, maximum 0.055. From the Jawa table of piston sizes (at right), it says the new piston-to-cylinder clearance is min 0.065, max 0.075 mm.

Piston Size Translator: When Jawa talks about piston size, their size is slightly less because pistons are slightly tapered. You have to add 0.02 mm to “Jawa” piston sizes to get “standard” piston sizes. Then the piston-to-cylinder clearance becomes 0.02 less, to min 0.045 max 0.055, more in agreement with Puch and most of the world. In inches it is 0.0017 to .0022 (one point seven thousandths to two point two thousandths). That clearance goes to near zero when the piston gets hot.

 

AssoASSO Pistons  ==========================

Asso Pistons

ASSO Pistons

Asso Factory

ASSO Factory

ASSO pistons were made in Italy mostly for Italian mopeds. ASSO stands for Assoluta Sicurezza Sempre Ovunque (Absolute Security Any time Anywhere). Early pistons said only “ASSO”, while later 1980’s ones said “ASSO.W”. Somehow ASSO merged with or was acquired by a German name, maybe some “kolben werke” to become ASSO Werke.

 

 

 

 

 

MahleCasal Pistons  ================================

Casal 40mm piston top

Casal Ø40 piston top says
<–saida       Mahle E logo
D,E,F are size increments
for Mahle nikasil cylinder

Casal 40mm piston bottom

Casal Ø40 piston bottom
says “Mahle            401”
made by Mahle for Casal

Casal Ø48 Piston top

Casal Ø48 Piston top
C,D,E are size increments

Casal Ø48 piston bottom

Casal Ø48 piston bottom
says “Mahle            481”

 

 

 

 

 

 

 

 

Casal (made in Portugal) pistons are made in Germany by Mahle. They say “saida” on top, exhaust side, Portuguese for “outlet”. They have an unusual flat bottom. They have a total height of 50mm. Top edge to pin is 23mm, plus pin 12mm, plus pin to bottom edge 15mm. There are two bore choices 40 and 48mm, each with several 0.01mm (micro!) increments to get a precise fit. A cylinder of letter “F” should get a matching “F” piston, unless it is worn, then maybe a “G” or even an “H” would be best. If the piston fit is too loose the engine will be weak, noisy, and fussy. Too tight and it will seize and do damage. Piston rings are both size 40 x 2.0 FG gap style, like Garelli. 

 

 

AssoGarelli Pistons =============================

Garelli piston markings

Garelli Pistons

 

 

 

Garelli 4th oversize 40.8mm piston, made by Asso, says “40.8”. You can see it’s bigger. Middle, Garelli standard 40.0mm piston, made by Asso, says “40” and “S”. The “S” means scoria, Italian for exhaust. Right, Garelli standard 40.0mm piston, aftermarket. All three are oriented with the exhaust side down, like in the engine.

 

Asso

Morini Pistons  =============================

Morini Pistons Nov 2013

Morini Pistons Nov 2013

 

 

Morini made a variety of 50cc engines. These pistons shown here are only for 1960’s to 80’s moped-type engines Morini MO, MO1, MO2, M1, MO2 foot shift, MO4, all 40.4mm. They also fit Verona, early Gyromat, and Benelli mopeds, originally 40.0mm, as an oversize. All of the rings and ring pin locations are the same.  Other Morini pistons 38.0, 39.0, and 46.0 are listed but not shown here.

 

 

 

 

 

 

 

 

 

Peugeot Pistons  ===============================Peugeot 1980 tiny

Peugeot 103 pistons have slightly different sizes.

Peugeot 103 pistons have slightly different sizes, aka “sorts”.
Left of the red line are the “standard” 40.0mm sorts A to II (39.88-39.98).
Right of the red line are the “oversize” 40.5mm sorts K to Q (40.45-40.50).
Upper half are chrome bore cylinders, pre-1979 with single letter sorts A to Q.
Lower half are nikasil bore cylinders, 1979-on with double letter sorts AA to II.

Peugeot 103 moped pistons are a very old design that has been in use at least since the 1950’s. The rings are thick, 2.5mm, like most old rings were. Peugeot 103 cylinders are all aluminum with a chrome plated (pre-1979) or nikasil plated (1979-on) cylinder wall. They expand along with the aluminum piston as they get hotter. Unlike a steel sleeve cylinder that fits slightly loose, when cold, and wiggles a tiny bit, these should be a light sliding fit, where the piston, without rings, pushes through by hand but does not fall through by it’s own weight. When the piston fit is too loose, it makes a tinkle sound when idling, and produces less torque. When it’s too tight, it simply won’t move easy, or at all, and when hot it will smear (melt off) the hot exhaust side and stick (seize). The procedure for “fitting” a Peugeot piston requires a flat stone cylinder hone (not a ball hone) for first making the cylinder wall flat by removing any high spots, and a Dremmel high speed rotary cutting tool for removing burrs from the edges of the ports, and a small round file for removing burrs and high spots from the piston, especially around the wrist pin holes. Sometimes just the act of pushing the wrist pin in and out will raise the corner edge and make the piston fit tighter. The bare piston is pushed into the cylinder in different ways. The high spots are located, by feel and sometimes vision, and removed. When all high spots are removed, and the piston still does not fall through under it’s own weight, then the fit is perfect.  Worn cylinders need slightly bigger pistons. So a worn “C” cylinder might need a D, E, or F piston. Badly worn or “gouged” cylinders need to be replaced (unless the gouges are lower than the exhaust port). Peugeot has made plenty of “oversize” (40.5mm instead of 40.0mm) pistons. But there are no 40.5 cylinders in California, only 40.0mm. That’s why Myrons Mopeds has 40.5 pistons but no cylinders. Too bad it’s expensive to bore out and re-plate a nikasil cylinder. It is an option, made possible by the half millimeter bigger pistons available.

 

 


Vespa (Piaggio) Moped Pistons ===================

Vespa moped “USA” piston and cylinder

Piaggio made their own pistons. All original pistons say Piaggio or have the logo on the inner side. They all have an arrow on top with the letters “SC”. That means “scoria”, Italian for “exhaust”. During installation, the arrow points toward the exhaust.

Ring gap: Piaggio specifies the ring gap to be 0.1 to 0.25 mm (0.004 to 0.010″)

10 or 12mm piston pins: All of the Vespa moped pistons below have 12mm wrist pins. There are some (as yet unknown) non-US models, probably Vespa clones, with 10mm wrist pins.

Piston versions: By having all of the Piaggio Parts Manuals, and especially the Parts Amendments 1, 2, 3 etc, it was possible to extract all of the Vespa (Piaggio) moped piston and ring part numbers. The millimeter sizes are not in any parts manual. They are from service manuals and actual parts new and used.

 

1974-76 Ciao
1967-76 Ciao (Euro)
1970-76 Boxer (Euro)
1976-78 Ciao
1977-78 Bravo
1978-80 Ciao
1978-80 Bravo
1978-79 Grande
1979-86+ Si
1980-86 Grande
1980-86+ Ciao, Bravo
piston std
upper ring
lower ring
112979
38.4 x 2.0 FG 77775
38.4 x 2.0 FG 77775
132521
38.4 x 2.0 FG 77775
38.4 x 2.0 FG 77775
182591 (says USA)
38.2 x 2.0 FG 166945
38.2 x 2.0 FG 166945
191034
38.2 x L-ring 182519
38.2 x 1.5 FG 182518
piston 1os
upper ring
lower ring
152381
38.6 x 2.0 FG 98196
38.6 x 2.0 FG 98196
137681
38.6 x L-ring 137690
38.6 x 1.5 FG 137693
182592 (most say 1M)
38.4 x L -ring G.68473
38.4 x 1.5 FG 132515
182592
38.4 x L-ring G.68473
38.4 x 1.5 FG 132515
piston 2os
upper ring
lower ring
152382
38.8 x 2.0 FG 98197
38.8 x 2.0 FG 98197
137682 (says 2M)
38.8 x L-ring 137691
38.8 x 1.5 FG 137694
182593
38.6 x L-ring 137690
38.6 x 1.5 FG 137693
182593
38.6 x L-ring 137690
38.6 x 1.5 FG 137693