Pistons

July 13, 2019

Look up or measure your piston’s pin size and upper length,
then scroll to that “pin-upper” section.

pin-upper 
12-22
AMF Roadmaster

12-18
Batavus with Laura M48 engine
12-17 Benelli 1965-1980
12-23 Casal K177, others
10-19 Columbia with Solo 255 engine
12-22 Columbia with Sachs 505 engine

12-18 Daelim DP50, DK50 engine
12-22 Demm Smily

12-17 Derbi Variant, TT, RD50 1974-1986
12-18 Derbi Variant Sport 1986-90
14-24 Flandria Bermuda
12-18 Garelli Eureka, Noi, Gulp, VIP
12-22 Garelli Monza GT

12-16 Hero Majestic mid-90’s
10-15 Honda PF50M, NQ50, SB50

10-20 Honda NC50, NA50, NU50, PA50
12-19 Honda NS50F
13-13 Indian AMI50 with PC50K1 re-make engine
14-18 Jawa Babetta 207 1970-83
12-16 Kawasaki AR50

12-20 Kinetic TFR with Piaggio re-make engine
12-19 Kreidler MP9, MP19
12-18 Laura M48, M56 engine

12-21 Minarelli V1L, V1HL engine
12-22 Minarelli V1, V1H engine
12-16 Morini MO1 MO2 MO4 M1 M101 w/alum fins
12-19 Morini MO1, MO2, M1 with iron cylinder fins

12-22 Morini S5K, S5K2, S5R, S5T engine
13-15 Motobecane 40, 50 with AV7 engine
10-19 Odyssey with Solo 254, 255 engine

12-16 Peugeot 102, 103 series
10-18 Puch MS50, others 50’s-60’s
12-17 Puch Maxi, others 1969-86
12-15 Rizzato 119 engine on Califfo
12-22 Sachs 504, 505 engine
10-18 Sears Allstate moped and early Puch

10-19 Solo 236, 237, 254, 255 engine
12-21 Suzuki FA50 Shuttle, FY50, FZ50
10-18 Tomos A3 engine 1974-91
12-17 Tomos A35 engine 1992-2006 (cyl says A5)
12-17 Tomos A55 engine 2002-18 (case says A52)

12-18 Trac 1981-86 with M56-remake engine
12-18 Trac 1984-90 with Daelim DP50 or DM50

10-19 TYM M48-remake engine on Angel, Speed Bird
12-20 Vespa (Piaggio) Ciao, Bravo, Grande, Si
10-21 Vespa (Piaggio) Ciao, Si (1990’s Euro)
10-20 Yamaha QT50 Yamahopper, PW50

 

50cc pistons for sale here are listed by “pin”, the wrist pin thickness, and “upper”, the distance from the pin edge to the top edge. Pin ranges from 10 to 14mm. Upper ranges from 13 to 23mm.

Pistons in the same section have the same upper and pin dimensions, and so can potentially interchange, if the bore and maybe other things are the same. That is why pistons are listed by size rather than name.

For example, an oversize Peugeot 103 piston 40.5mm is perfect for a worn 40.4mm Morini MO1, after honing. They are both 12 pin and 16 upper, in the 12-16 section.

Abbreviations and Notes:
Piston actual diameter is measured at skirt (bottom), where it is largest.
All new pistons come with new rings, clips and pin, unless noted.
gap GN grano normale means side pin gap style (aka FG foro grano)
gap GI  grano interno means center pin gap style  

“x” means that digit of the number is unknown

pin up  lo bore M#   skirt   ring1   ring2  maker  price
pin is the piston pin diameter (in mm)
up is upper distance from pin to top edge
lo is lower distance from pin to bottom
bore is the cylinder diameter
M# is the Myrons encoded part number
skirt is the skirt diameter at bottom
ring1 is the upper piston ring specification
ring2 is the lower piston ring specification

c is rectangular cross-section, common gap style
i is rectangular cross-section, internal gap style
t is trapezoidal (slanted top), either gap style

L is L-shaped (aka Dykes), L-ring gap style

 



10-15 

40.00 for ’73-78 Honda PF50M 
pin up  lo bore M#  skirt  ring1  ring2  price
10-15-20-40.00-0 39.95 t1.5n c1.5n  n.a. Honda 13101.122.003

41.00 for ’84-87 Honda NQ50 Spree  
00.0 and ’88-90 Honda SB50 Elite

pin up  lo bore M#  skirt  ring1  ring2  price
10-15-20-41.00-0 40.95 t1.5n c1.5n  n.a. Honda 13101-GK8-780
10-15-20-41.00-0 40.95 t1.5n c1.5n  n.a. and 13101-GS6-505
10-15-20-41.25-0 41.20 t1.5n c1.5n  n.a. Honda 13106-GK8-780
10-15-20-41.50-0 41.45 t1.5n c1.5n  n.a. Honda 13107-GK8-780

 



10-16.5 

41.00 for ?? 
pin up  lo bore M#  skirt  ring1  ring2  price
10-16.5-16-41.00-0 40.94 c1.5i c1.5i  $65 Meteor

 

 



10-18

38.0 – 38.5 for ’74-91 Tomos A3 
pin up  lo bore M#  skirt  ring1  ring2   price  maker part#
10-18-24-38.00-0 37.94 c2.0n c2.0n  n.a. 20mph
10-18-21-38.00-0 37.94 c2.0n c2.0n  n.a. 25mph 207407
10-18-19-38.00-0 37.94 c2.0n c2.0n  $50 30mph 207403
10-18-19-38.00-1 37.95 c1.5n c1.5n  $60 generic
10-18-18-38.00-0 37.95 c2.0n c2.0n  n.a. generic
10-18-19-38.50-0 38.45 c2.0n c2.0n  n.a. Mahle  202420


10-18

38.0 for 50’s-60’s Sears Allstate (Puch)
10-18-19-38.00-2
37.9x c2.0n c2.0n  n.a. Mahle 0501.1006.2
10-18-19-38.00-G
37.95 c2.0n c2.0n  n.a. GOL 0567

Tomos A3 pistons have different skirt lengths for each US speed version. A longer piston skirt opens the intake port later and closes it sooner, so it gulps less air with each revolution. That makes more torque at low rpm and less torque at high rpm. The 1.0 hp (20 mph) piston is 55 tall, 52 at edge = 24+10+18, 24 mm at skirt. The 1.5 hp (25mph) piston is 52 tall, 49 at edge = 21+10+18, 24 at skirt. The 2.0 hp (30 mph) piston is 50 tall, 47 at edge = 19+10+18, 24 at skirt.

 



10-19

38.0 for 1976-80 Solo on Odyssey, Columbia
pin up  lo bore M#  skirt  ring1 ring2 maker  price 
10-19-22-38.00-N 37.9x c1.5n c1.5n Mahle   none 2200593 “N”
10-19-22-38.00-U
37.9x c1.5n c1.5n Mahle   none 2200600 “U”


10-19  Angel and Batavus pistons

40.0 for 1977-84 TYM Angel
10-19-15-40.00-0 39.92 c1.5n c1.5n generic none

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.

 



10-20.5 Honda NC50 and PA50 piston new

40.0 for 1977-83 Honda NC50 
pin up  lo bore M#  skirt  ring1 ring2 maker   price
10-20-18-40.00-0 39.95 t1.5n c1.5n Honda   none  13101.147.000
10-20-18-40.00-1 39.96 t1.5n c1.5n generic   $55
40.0 for 1978-83 Honda PA50 (same but with decomp cut)
10-20-18-40.00-2 39.95 t1.5n c1.5n Honda   none  13101.148.010
10-20-18-40.00-1 39.96 t1.5n c1.5n generic   $55


10-20.5 20mm upper (10mm pin) Yamaha QT50 & PW50

40.0 for 1979-87 Yamaha QT50 PW50
10-20-17-40.00-0 39.9x t1.5n c1.5n Yamaha none 3L5.11630.00.00

 


10-21 21mm upper, 10 pin, Vespa Euro models

38.2 for ’84-on Piaggio Ciao, Si
pin up  lo bore M#  skirt  ring1 ring2  maker  price
10-21-17-38.20-0 38.13 L2.0nc1.5n Meteor  $60 


10-21 21mm upper, 10mm pin Chinese scooters

40.0 – 40.25 for 2000’s Eton (Chinese scooter) 
10-21-18-40.00-0 39.9x t1.2n t1.2n generic $60 632964
10-21-18-40.25-0 40.1x t1.2n t1.2n generic $60 632965

 



12-15

39.4 for Rizzato 119 engine on Califfo, Atala
pin up  lo bore M#  skirt  ring1 ring2  maker  price
12-15-23-39.40-0 39.33 c2.5n c2.5n generic  $35 no rings
12-15-23-39.80-0 39.73 c2.5n c2.5n generic  none

This is an unusual design from the 1950’s, with the highest wrist pin. That allows transfer flow through the lower part of the piston, instead of around the sides completely. The top crown of the piston is a normal shallow dome, but with three equal large “bites” taken out of it. 



12-16

39.0 for ’82 Kawasaki AR50
pin up  lo bore M#  skirt  ring1 ring2  maker  price
12-16-18-39.00-0 38.95 t1.2n t1.2n generic none 13001.1074


12-16 

40.0 for ’70’s Peugeot 103, 102
pin up  lo bore M#  skirt  ring1 ring2 maker  price 

12-16-17-39.91-A 39.88 c2.5i c2.5i Peugeot $70   69707 Sort A
12-16-17-39.92-B 39.89 c2.5i c2.5i Peugeot $70   69708 Sort B
12-16-17-39.93-C 39.90 c2.5i c2.5i Peugeot $70   69709 Sort C (=AA)
12-16-17-39.94-D 39.91 c2.5i c2.5i Peugeot none 69710 Sort D (=BB)
12-16-17-39.94-0 39.91 c2.5i c2.5i GOL       $60   replica Sort D (=BB)
12-16-17-39.95-E 39.92 c2.5i c2.5i Peugeot $70   69711 Sort E (=CC)
12-16-17-39.96-F 39.93 c2.5i c2.5i Peugeot $70   69712 Sort F (=DD)
12-16-17-39.96-0  39.93 c1.5i c2.5i generic  $70   MF553-F
12-16-17-39.97-G 39.94 c2.5i c2.5i Peugeot $70   69713 Sort G (=EE)
12-16-17-39.98-H 39.95 c2.5i c2.5i Peugeot $70   69714 Sort H (=FF)
12-16-17-39.98-0  39.95 c2.5i c1.5i generic  $70   MF553-C
12-16-17-39.99-I  39.96 c2.5i c2.5i Peugeot none 69715 Sort I (=GG)
12-16-17-40.00-J  39.97 c2.5i c2.5i Peugeot none 69715a Sort HH
12-16-17-40.01-ii 39.98 c2.5i c2.5i Peugeot none 69715b Sort II


12-16

40.0 ’90’s Hero Pacer, Panther
12-16-17-40.00-1 39.9x c2.0n c2.0n generic none

12-16

40.0 ’00’s Yumbo Free, Sport
12-16-17-40.00-1 39.9x c1.5n c1.5n generic none

 

 

 


Morini MO1 and MO2 pistons have a cut-out on the bottom intake side. It can be different heights 0, 3 or 5 mm. That’s what “cut=3” means. Inside the piston is an ID mark, such as “ASSO 1929”. This can tell the piston type but not the size. 

 

12-16

40.0 ’68-77+ Morini Gyromat, Gyrokick,
40.0 Morini Convert, Malaguti Duomatic

40.0 MO, MO4 with 1970-type aluminum cylinder
pin up  lo bore M#  skirt ring1 ring2  price  part#  cut  says

12-16-17-40.00-0 39.92 c1.5i c1.5i none 23-01xx 3 ASSO

12-16 16mm upper height pistons Peugeot left and Morini right 

40.4 – 41.0 ’77-80+ Morini Gyromat, Convert, Gyrokick,
40.0 – 41.0 MO1, MO2, MO4 with 1977-type aluminum cylinder

12-16-17-40.40-2 40.33 c1.5i c1.5i $60 0089 00    3 GOL
12-16-17-40.40-3 40.32 c1.5i c1.5i n.a. 23.0125    3 ASSO 1929
12-16-17-40.40-4 40.32 c1.5i c1.5i n.a. 23.0125    3 ASSO.W 2352
12-16-17-40.40-0 40.35 c1.5i c1.5i $70 23.0125    5 ASSO.W 2351
12-16-17-40.40-1 40.35 c1.5i c1.5i $60 23.0125    3 says nothing
12-16-17-40.60-0 40.53 c1.5i c1.5i $72 23.0126/6 3 ASSO 1929
12-16-17-40.80-0 40.72 c1.5i c1.5i $70 23.0126/8 3 ASSO 1929
12-16-17-41.00-0 40.90 c1.5i c1.5i $74 23.0126/0 3 says nothing
40.4 – 40.8 ’78-90 Morini M1, M101
40.0 with 1980-type aluminum cylinder, case reed induction

12-16-17-40.40-5 40.32 c1.5i c1.5i n.a. 23.0134     0 ASSO W 1929M1
12-16-17-40.60-1 40.5x c1.5i c1.5i n.a. 23.0135/6 0 ASSO W 1929M1
12-16-17-40.80-1 40.7x c1.5i c1.5i n.a. 23.0135/8 0 ASSO W 1929M1
40.4 ’78-90 Morini MO4
12-16-17-40.40-L 40.33 L2.0  c1.5i n.a. 23.01??  3 ASSO 1929MO4


40.5 for some ’70’s Peugeot 
12-16-17-40.47-K 40.44 c2.5i c2.5i $60 69716 Peugeot sort K
12-16-17-40.48-L  40.45 c2.5i c2.5i $60 69717 Peugeot sort L
12-16-17-40.49-M 40.46 c2.5i c2.5i $60 69718 Peugeot sort M
12-16-17-40.50-N 40.47 c2.5i c2.5i $60 69719 Peugeot sort N
12-16-17-40.51-P  40.48 c2.5i c2.5i $60 69720 Peugeot sort P
12-16-17-40.52-Q 40.49 c2.5i c2.5i $60 69721 Peugeot sort Q

 

Peugeot 103 pistons have slightly different sizes.

Myron’s Peugeot pistons, cylinders and sorts:
Left of the red line are the 40.0mm sorts A to II (39.88-39.98).
Right of the red line are the 40.5mm sorts K to Q (40.45-40.50).
Upper cylinders are pre-1979 chrome bore, sorts A to Q.
Lower cylinders are 1979-on nikasil bore, 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.

 



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

36.5 for 03 Tomos A35 engine on MC36 (36 cc off-road)
pin up  lo bore M#  skirt  ring1 ring2  price   part#
12-17-18-36.50-0 36.43 c1.5n c1.5n $55   229803 Vertex
38.0 – 38.5 for 91-06 A35 engine (all-iron cylinder)
12-17-18-38.00-A 37.95 c1.5n c1.5n none 409000 generic
12-17-18-38.00-B 37.95 c1.5n c1.5n $65   223747 Vertex
12-17-18-38.50-0 38.4x c1.5n c1.5n none 227334 Vertex
12-17-18-38.50-1 38.4x c1.5n c1.5n $60   409001 generic

12-17    

38.0 for 04-06 A55 engine (alum. cyl, trapezoidal rings)
12-17-21-37.96-A 37.94 t1.5n  t1.5n none 233709 Vertex
38.0 for 06-18 A55 engine (alum. cyl, rectangular rings)
12-17-21-37.97-B
37.95 c1.5n c1.5n $65   233709 14140 37.97
12-17-21-37.98-C
37.96 c1.5n c1.5n none 233709 14140 37.98

 


12-17  

Original Puch pistons are made in Austria by Elko. 

Original Pistons on US Models 1976-86

1976-77 1.0 hp Maxi 349.110.0060 use 349.110.0069
1978-85
1.0 hp plain Maxi, Rigid (hardtail) 

7-fin cylinder, Elko piston, 2-rings 2.0
pin up lo ∅cylinder ∅piston 0 Puch part#   price  ID marks

12-17-26-37.98-1
37.95 349.110.0069/21 n.a. 38 1
12-17-26-37.99-1 37.96 349.110.0069/22 n.a. 38 2
12-17-26-38.00-1 37.97 349.110.0069/23 n.a. 38 3
12-17-26-38.01-1 37.98 349.110.0069/24 n.a. 38 4
12-17-26-38.02-1 37.99 349.110.0069/25 n.a. 38 5

1976-77 1.5-2.0 Maxi 349.110.1060 use 349.110.1069
1978-85
1.5-2.0 hp plain Maxi, Rigid, JC Penney Pinto

7-fin cylinder, Elko piston, 2-rings 2.0
pin up lo ∅cylinder ∅piston 0 Puch part#   price  ID marks

12-17-21-37.98-1
37.95 3
49.110.1069/21 $72 38 1 1019
12-17-21-37.99-1
37.96 3
49.110.1069/22 n.a. 38 2 1019
12-17-21-38.00-1
37.97 3
49.110.1069/23 n.a. 38 3 1019
12-17-21-38.01-1
37.98 3
49.110.1069/24 $58 38 4 1019
12-17-21-38.01-1
37.98 3
49.110.1069/24 $72 38 4 1019
12-17-21-38.02-1
37.99 3
49.110.1069/25 $75 38 5 1019

1977-78? (Euro deluxe) 349.210.5060 use 349.210.5069
1
978-84
1.5-2.0 hp Maxi Luxe, Sport, Newport

8-fin cylinder, Elko piston, 2-rings L+2.0
pin up lo ∅cylinder ∅piston 0 Puch part#   price  ID marks

12-17-23-38.00-L
37.95 349.210.5069/11 n.a. 38 00 1 1593a
12-17-23-38.01-L 37.96 349.210.5069/22 $49 38 00 2 1593a
12-17-23-38.02-L 37.97 349.210.5069/33 n.a. 38 00 3 1593a
12-17-23-38.25-L
38.19 349.310.4669/03 n.a. 38.25 1 1593a
12-17-23-38.26-L 38.20 349.310.4669/04 n.a. 38.25 2 1593a

1978-79 1.0-2.0 hp Sears Free Spirit use 349.110.1069
7-fin cylinder, Mahle piston, 2-rings 2.0
pin up lo ∅cylinder ∅piston 0 Sears part#  price  ID marks

12-17-21-37.98-S
37.95 000000000 3109
n.a.   1 
12-17-21-37.99-S
37.96 000000000 3110 n.a.   2

12-17-21-38.00-S
37.97 000000000 3111 n.a.   3

12-17-21-38.01-S
37.98 000000000 3112 n.a.   4

12-17-21-38.02-S
37.99 000000000 3113 n.a.   5

1978-82 1.5-2.0 hp Puch Magnum
9-fin cylinder, Elko piston, 2-rings 2.0
pin up lo ∅cylinder ∅piston 0 Puch part#   price  ID marks

12-17-23-38.00-1
37.95 350.310.0069/03 $52 38 00 1 1116
12-17-23-38.01-1 37.96 350.310.0069/04 $50 38 00 2 1116
12-17-23-38.25-1
38.19 350.310.0669/03 n.a. 38.25 1 1116
12-17-23-38.26-1 38.20 350.310.0669/04 n.a. 38.25 2 1116

In ’84 the ∅14 piston pin bushing became a ∅15 needle bearing.
The ’84 2-ring piston 345.410.0069 had no wrist pin oil holes.
That soon changed to a 1-ring piston with 4 oil holes.

1984 1.5-2.0 hp Maxi Sport LS to-2421596
8-fin cylinder, Elko piston, 2-rings 2.0+2.0, no oil holes
pin up lo ∅cylinder ∅piston 0 Puch part#   price  ID marks

12-17-23-38.01-L
37.96 345.410.0069/13 n.a. 38  D 
12-17-23-38.02-L 37.97 345.410.0069/14 n.a. 38  E 
12-17-23-38.03-L 37.98 345.410.0069/15 n.a. 38  F

1984-86 1.5-2.0 hp Austro Daimler (Maxi+)
8-fin cylinder, Elko piston, 1-ring 2.0, 4 oil holes
pin up lo ∅cylinder ∅piston 0 Puch part#   price  ID marks

12-17-23-37.99-C
37.94 345.110.0069/11 n.a. 38 00 B 1734
12-17-23-38.00-C 37.95 345.110.0069/12 $72 38 00 C 1734
12-17-23-38.01-C 37.96 345.110.0069/13 n.a. 38 00 D 1734
1984-86 1.5-2.0 hp LS 2421597-on, Cobra to-1505807
12-17-23-38.01-C 37.96 345.110.0069/13 n.a. 38 00 D 1734
12-17-23-38.02-C 37.97 345.110.0069/14 n.a. 38 00 E 1734
12-17-23-38.03-C 37.98 345.110.0069/15 n.a. 38 00 F 1734

12-17-23-38.25-C
38.19 345.110.0669/11 n.a. 38.25 B 1734
12-17-23-38.26-C 38.20 345.110.0669/12 n.a. 38.25 C 1734

1985-86 1.5-2.0 hp Cobra 1505808-on
8-fin cylinder, Elko piston, 2-rings 1.5+1.5
pin up lo ∅cylinder ∅piston 0 Puch part#   price  ID marks

12-17-23-37.99-A
37.94 349.110.6069/11 n.a. 38  1
12-17-23-38.00-A 37.95 349.110.6069/12 n.a. 38  2
12-17-23-38.01-A 37.96 349.110.6069/13 n.a. 38  3

 

Aftermarket Puch Pistons

Pistons include rings, pin and clips.


0 pin up lo ∅cylinder ∅piston rings length 12+17+15.0+3.0=47.0
1 12-17-15-38.00-A 37.93 2.0+2.0 $30 406300 1990’s AR

2 12-17-15-38.50-A 38.45 2.0+2.0 $30 203200 1990’s AR
0 pin up lo ∅cylinder ∅piston rings length 12+17+18.0+3.5=50.5
3 12-17-18-38.00-A 37.94 2.0+2.0 $35 406300 ’00’s Step II
4 12-17-18-38.00-G 37.95 2.0+2.0 n.a. 0566      GOL
5 12-17-18-38.00-2  37.95 L2 +2.0 n.a. 0568      GOL
6 12-17-18-38.00-1  37.95 L2 +0.0n.a. 0568C    GOL

0 pin up lo ∅cylinder ∅piston rings length 12+17+20.0+3.5=52.5

7 12-17-20-37.98-G 37.95 L2 +2.0n.a. 0038A-A GOL
7 12-17-20-37.99-G 37.96 L2 +2.0 n.a. 0038A-B GOL
7 12-17-20-38.00-G 37.97 L2 +2.0n.a. 0038A-C GOL
7 12-17-20-38.01-G 37.98 L2 +2.0n.a. 0038A-D GOL
0 pin up lo ∅cylinder ∅piston rings length 12+17+20.5+3.0=52.5

8 12-17-21-38.25-A 38.17 2.0+2.0 $50 203200 ’10’s Step II
9 12-17-21-38.00-0 37.95 1.5+1.5 $60 thereal1.5  treatland
0 pin up lo ∅cylinder ∅piston rings length 12+16.5+23+3.5=55.0

10 12-17-23-37.94-G 37.92 2.0+2.0n.a. 0037A-A GOL “37.95”
10 12-17-23-37.95-G 37.93 2.0+2.0 n.a. 0037A-B GOL “37.96”
10 12-17-23-37.96-G 37.94 2.0+2.0$60 0037A-C GOL “37.97”
10 12-17-23-37.97-G 37.95 2.0+2.0 n.a. 0037A-D GOL “37.98”
10 12-17-23-37.98-G 37.96 2.0+2.0n.a. 0037A-E GOL “37.99”
10 12-17-23-37.99-G 37.97 2.0+2.0$60 0037A-F GOL “38.00”
10 12-17-23-38.00-G 37.98 2.0+2.0$60 0037A-G GOL “38.01”
10 12-17-23-38.01-G 37.99 2.0+2.0$60 0037A-H GOL “38.02”

Here the pistons are listed in order of increasing skirt length 15 to 23 mm. On a piston ported two stroke engine, a longer piston skirt, on the intake side, opens the intake port later and closes it sooner than a shorter skirt. That lower intake duration helps prevent back flow at low rpm, but limits forward flow at high rpm. So for the same cylinder, a longer piston skirt gives a faster take-off but a slower top speed. A shorter skirt gives a slower take off and a faster top speed.

Different cylinders can have the intake port lower or higher, so the cylinder matters when choosing a replacement piston skirt length. Look in the original pistons what the skirt length was originally for your cylinder version. Choose one with the same length for the same power curve.

 


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

38.0 – 38.9 for 74-86 Derbi (pyramid reed and non-reed)
steel-sleeve aluminum cylinder, rings L2.0 and c1.5n
pin up  lo bore M#  skirt  price     Derbi#    markings

12-17-23-38.00-D 37.95 $68 000.802.5090 says B or B9
12-17-20-38.25-D 38.18 $40
000.802.5091 0.25 B or 0.25 C
12-17-20-38.25-D 38.18 $35 000.802.5091 38.205 JG 0.045
12-17-20-38.40-D 38.3x n.a. 000.802.5092
12-17-20-38.70-D 38.6x n.a. 000.802.5093
12-17-20-38.90-D 38.8x n.a. 000.802.5094
steel-sleeve aluminum cylinder, rings L2.0 and L2.0
12-17-20-38.25-ll 38.18 $30 000.802.5091 both L-rings!


12-17 17mm upper, 12 pin, Benelli 

40.00 – 40.40 for ’65-80 Benelli
12-17-18-40.00-0 39.9x c1.5n c1.5n n.a. 70.06.04.00=G7346
12-17-18-40.00-G 39.95 c1.5n c1.5n $65 GOL 0504
12-17-18-40.20-0 40.1x c1.5n c1.5n n.a. 70.06.04.02=G7346/2
12-17-18-40.40-0 40.3x c1.5n c1.5n n.a. 70.06.04.04=G7346/4


12-17

40.00 – 40.25 for unknown Yamaha 
12-17-19-40.00-0 39.94 t1.5n  t1.5n $60   model?  complete
12-17-19-40.25-0 40.22 t1.5n  t1.5n $30   model?  no rings

 



12-18 

40.0 – 40.25 for Laura M48 engine on 72-80 Batavus
pin up  lo bore M#  skirt  ring1 ring2  maker  price
12-18-14-40.00-0 39.95 c1.5n c1.5n Mahle  n.a. 480580 says 39.95
12-18-14-40.25-0 40.20 c1.5n c1.5n Mahle  $75 480581 1os 

12-18 

 

40.0 for Laura M56 engine on 78-80 Batavus, 81-86 Trac
pin up  lo bore M#  skirt  ring1 ring2  maker  price
12-18.5-17-40.00-G 39.94 c2.0n c2.0n GOL  $60 0037
12-18.0-14-39.98-A 39.96 c1.5n c1.5n Mahle  n.a. 80016 says A
12-18.0-14-39.99-B 39.97 c1.5n c1.5n Mahle  n.a. 80017 says B

12-18.8-17-39.97-G 39.97 c2.0n c2.0n GOL   $60 0534 C
12-18.8-17-39.98-G 39.98 c2.0n c2.0n GOL   $60 0534 D

12-18.0-14-40.00-C 39.98 c1.5n c1.5n Mahle  n.a. 80018 says C
12-18.0-14-40.01-D
39.99 c1.5n c1.5n Mahle  n.a. 80019 says D
12-18.0-14-40.02-E 40.00 c1.5n c1.5n Mahle  n.a. 80020 says E

 

 


12-18  

40.0 for  86-89+ Derbi (flat reed)
12-18-19-39.97-A 39.945c1.5i  c1.5i Mahle  n.a. 0F0.250.0091/A
12-18-19-39.97-B 39.950c1.5i  c1.5i Mahle  n.a. 0F0.250.0091/B
12-18-19-39.98-C 39.955c1.5i  c1.5i Mahle  n.a. 0F0.250.0091/C
12-18-19-39.98-D 39.960c1.5i  c1.5i Mahle  n.a. 0F0.250.0091/D
12-18-19-39.99-E 39.965c1.5i  c1.5i Mahle  n.a. 0F0.250.0091/E


12-18.5

40.0 for Daelim DP50, DK50 engines on 84-90 Trac
pin up  lo bore M#  skirt    ring1 ring2  maker  price
12-18.5-14-39.99-0 39.97   t1.5n  t1.5n original n.a. sort A
12-18.5-14-39.99-5 39.975 t1.5n  t1.5n original n.a. sort B
12-18.5-14-40.00-0 39.98   t1.5n  t1.5n original n.a. sort C
12-18.5-14-40.00-5 39.985 t1.5n  t1.5n original n.a. sort D
12-18.8-17-39.97-G 39.97  c1.5n  c1.5n GOL     $60 0534 C
12-18.8-17-39.98-G 39.98  c1.5n  c1.5n GOL     $60 0534 D


12-18.5 18mm upper, 12 pin, Garelli

40.0 – 40.8 for 70-90 Garelli H1 (iron cylinder)
pin up  lo bore M#  skirt   price  maker    part#   speed version
rings c2.0n c2.0n        length = 12+18.5+15.5+3.0=49.0

12-18.5-16-40.00-0 39.93  n.a. generic
12-18.5-16-40.00-1 39.92   $50 generic good-used
12-18.5-16-40.00-0 39.9x  n.a. Asso 200001.2.150  20/30

12-18.5-16-40.20-0 40.1x  n.a. Asso 200001.2.151  20/30
12-18.5-16-40.40-0 40.3x  n.a. Asso 200001.2.152  20/30
12-18.5-16-40.60-0 40.5x  n.a. Asso 200001.2.153  20/30
12-18.5-16-40.80-0 40.7x  n.a. Asso 200001.2.154  20/30
rings c2.0n c2.0n        length = 12+18.5+16.5+3.0=50.0

12-18.5-17-40.00-0 39.9x  n.a. Asso 205053.2.150  25mph
12-18.5-17-40.00-G 39.94  $60 GOL 0037

12-18.5-17-40.20-0 40.1x  n.a. Asso 205053.2.151  25mph
12-18.5-17-40.40-0 40.3x  n.a. Asso 205053.2.152  25mph
12-18.5-17-40.60-0 40.5x  n.a. Asso 205053.2.153  25mph
12-18.5-17-40.80-0 40.7x  n.a. Asso 205053.2.154  25mph

12-18.8

40.0 for 78-90 Garelli (flat top for alum. cylinder)
rings c2.0n c2.0n        length = 12+18.8+16.7+0.0=47.5
pin up  lo bore M#  skirt   price  maker    part#   speed version

12-18.8-1x -40.00-0 39.9x  n.a. Asso 205058.2.150 20/25
12-18.8-17 -40.00-0 39.9x  n.a. Asso 205088.2.150 30mph
12-18.8-17 -39.95-G 39.95  n.a. GOL 0534 A
12-18.8-17 -39.96-G 39.96  n.a. GOL 0534 B
12-18.8-17 -39.97-G 39.97  $60 GOL 0534 C
12-18.8-17 -39.98-G 39.98  $60 GOL 0534 D
12-18.8-17-40.40-G 40.33  $55 GOL 0534

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.

 



12-19  

39.0 – 39.75 for 1990 Honda NS50
pin up  lo bore M#  skirt  ring1 ring2  maker  price

12-19-16-39.00-0 38.94 t1.2n c1.2n  generic none 13101-GE2-305
12-19-16-39.25-0 39.19 t1.2n c1.2n  generic none 13102-GE2-305
12-19-16-39.50-0 39.44 t1.2n c1.2n  generic none 13103-GE2-305
12-19-16-39.75-0 39.69 t1.2n c1.2n  generic none 13104-GE2-305


12-19  

40.0 for  1970’s Kreidler Flory rings c1.5i  c1.5i
pin up  lo bore M#  skirt  maker  price    part#     ID marks 

12-19-15-39.98-D 39.93 Mahle none 2150383d R021 40154+
12-19-15-39.99-E 39.96 Mahle none 2150383f  R021 40154+
12-19-15-40.00-H 39.97 Mahle $35 2150383h (worn used)
12-19-15-40.01-K
 39.98 Mahle $65 2152387k  R041 40154+
12-19-15-40.02-M 39.99 Mahle $65 2152387m R041 40154+

2150383 and 2152387 are the same except for piston pin oil holes.


12-19.5  

40.4 – 40.8 ’75-80 Morini MO1, MO2 with all-iron cylinder
rings c1.5i  c1.5i 
pin up  lo bore M#    skirt  maker  price  part#   ID marks
12-19-17-40.40-0  40.32 Asso     n.a. 23.0130   Asso 2139
12-19-17-40.40-2  40.32 GOL      $63 GOL 0307  cut=4

12-19-17-40.60-0  40.5x Asso     n.a. 23.0131/6 Asso 2139
12-19-17-40.80-0  40.7x Asso     n.a. 23.0131/8 Asso 2139

40.4 – 40.8 ’78-80 Morini M1 (reed) with all-iron cylinder
rings c1.5i  c1.5i 
pin up  lo bore M#    skirt  maker  price  part#   ID marks
12-19-17-40.40-2  40.32 GOL      $63 GOL 0307  cut=4

12-19-17-40.40-1  40.3x Asso     n.a. 23.0136 
12-19-17-40.60-1  40.5x Asso     n.a. 23.0137/6
12-19-17-40.80-1  40.7x Asso     n.a. 23.0137/8

 



12-20 

38.4 1995-05 Kinetic TFR (Boxer remake)
pin up  lo bore M#  skirt  maker  price  rings t1.5n  t1.5n

12-20-16-38.40-K 38.30  generic n.a. no arrow
12-20-16-38.40-G 38.3x  GOL     n.a. 0095


12-20 20mm upper, 12 pin, China two stroke

40.0 2000’s China 49cc 
pin up  lo bore M#  skirt  maker  price  rings t1.2n  t1.2n

12-20-17-40.00-0 39.9x  generic $60 633992


12-20.5 20mm upper, 12mm pin, Vespa   

38.4 – 38.8 for ’67-78 Ciao, 70-78 Boxer, 77-78 Bravo
pin up  lo bore M#  skirt  maker  price rings c2.0n c2.0n
12-20-16-38.40-V 38.3x 
Piaggio $50 112979=132521
12-20-16-38.40-G 38.3x  GOL     n.a. 0095

12-20-16-38.60-V 38.54  Piaggio n.a. 152381=137681 says 1M
12-20-16-38.60-G 38.5x  GOL     n.a. 0095

12-20-16-38.80-V 38.74  Piaggio $60 152382=137682 says 2M

12-20.5

38.2 – 38.6 for ’78-80 Ciao, Bravo, Grande (USA only)
pin up  lo bore M#  skirt  maker  price rings c2.0n c2.0n
12-20-16-38.20-V 38.12  Piaggio $60 182591 says USA
12-20-16-38.20-G 38.1x  GOL     n.a. 0095
pin up  lo bore M#  skirt  maker  price rings L2.0   c1.5n
12-20-16-38.40-L 38.32  Piaggio $65 182592 says 1M
12-20-16-38.40-G 38.3x  GOL     n.a. 0096

12-20-16-38.60-L 38.54  Piaggio n.a. 182593 says 2M
12-20-16-38.60-G 38.5x  GOL     n.a. 0096

12-20.5 20mm upper, 12 pin, Vespa L-ring

38.2 – 38.6 for ’79-84 Si, 80-84 Ciao, Bravo, Grande 
pin up  lo bore M#  skirt  maker  price  rings L2.0   c1.5n
12-20-16-38.20-L 38.1x  Piaggio n.a. 191034
12-20-16-38.20-G 38.1x  GOL     n.a. 0096
12-20-16-38.20-A 38.12  Asso    $60 3517
12-20-16-38.40-G 38.3x  GOL     n.a. 0096
12-20-16-39.60-A 39.53  Asso    $48 3517

1984 pin reduction: In 1984 the Piaggio piston pin changed from 12 to 10 mm. So the piston changed from 12-20 to 10-21. See 10-21 above. Because Piaggio moped sales were low in 1984, and ended in 1986, there were almost no US models with 10 mm piston pins. 99% of US models had 12mm pins. But in Europe and other countries like Japan, Piaggio moped sales continued into the 1990’s. So bikes in those countries have either 12 or 10 mm piston pins. 

1978 bore reduction: In 1978 on US models the bore was reduced from 38.4 to 38.2mm. Some ’78’s have a 38.4 bore, and some have a 38.2 bore. Same thing happened to Minarelli at that same time (a reduction from 38.8 to 38.7). The pistons changed because of legal requirements.

1979-80 L type ring: In 1979-80 the upper piston ring changed from common (rectangular) to L shape, aka Dykes. The lower ring changed thickness from 2.0 to 1.5 mm. Some ’79’s had common top rings, and some had Dykes. Oversize Piaggio pistons already had Dykes upper rings since about 1977. The Dykes ring style was also adopted by Derbi in the mid-70’s and others in the late 70’s. It was mainstream in 1979! But by the mid-1980’s L-rings became out of style and obsolete. They did cost more to make, and broke easier. There was not much benefit. So all 90’s and later two-stroke moped engines have rectangular or trapezoidal top rings, mostly thinner than older designs.  

1978-80 changes: Vespa (Piaggio) standard pistons changed in 1978 and 1979-80. Bikes made during those years can have either the older or the newer piston. There is no way to tell by ID numbers.

SC means exhaust (scoria): All original pistons are made by Piaggio and 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. Vespa pistons have skirt cut-outs rotated 30 deg.

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

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.

 



12-21 21mm upper, 12 pin, Suzuki FA50

41.0 for Suzuki FA50 FS50 FZ50
pin up  lo bore M#  skirt  ring1 ring2  maker  price
12-21-15-41.00-0 40.92 t1.5n  t1.5n Suzuki n.a. 12110.43000
12-21-15-41.50-0 41.4x t1.5n  t1.5n Suzuki n.a. 12100.35611.050
12-21-15-42.00-0 41.9x t1.5n  t1.5n Suzuki n.a. 12100.35611.100

 



12-22  22mm upper, 12 pin, Sachs 504/505  

38.0 – 38.6 for Sachs 504, 505 1A, 1B
pin up  lo bore M#  skirt  ring1 ring2  maker  price
12-22-16-38.00-A 37.95 c2.0n c2.0n AMF     $60
original AMF BHE900, says 38
12-22-16-38.00-0 37.95 c2.0n c2.0n Meteor $60 sort B says Z21  38

12-22-17-38.00-0 37.96 c2.0n c2.0n Mahle   n.a. 0286-378-005 Sachs  552 says 37.98 G8
12-22-17-38.00-4 37.94 c2.0n c2.0n Meteor n.a. PC0922A for 37.97
12-22-17-38.00-5 37.95 c2.0n c2.0n Meteor n.a. PC0922B for 37.98
12-22-17-38.00-6 37.96 c2.0n c2.0n Meteor $60 PC0922C for 37.99

12-22-17-38.00-7 37.97 c2.0n c2.0n Meteor $60 PC0922D for 38.00
12-22-17-38.30-1 38.25 c2.0n c2.0n xxxxxx $65 says 38.28
12-22-17-38.60-1 38.55 c2.0n c2.0n xxxxxx $60 says 38.58

38.0 – 38.6 for Sachs 504, 505 1C, 1D
pin up  lo bore M#  skirt  ring1 ring2  maker  price
12-22-14-38.00-0 37.95 c1.5n c2.0n Mahle  n.a. 0286-378-051  Sachs 504,505 1C,1D  553
12-22-14-38.00-1 37.95 c1.5n c2.0n generic $55 406500 Sachs 504,505 1C,1D  says 38
12-22-14-38.60-0 38.55 c1.5n c2.0n Mahle  n.a. 0286-378-052 1os Sachs 504,505 1C,1D

 


12-22 Pistons

bore  pin upper lower dome total  Minarelli#
over-sizes 
engines it was original on
pin up  lo bore M#  skirt  price  Minarelli# 0 MMI#  bare#

 

1. For stroke 42, all-iron cylinder, piston port intake

38.00 12+22+15.5+3.5=53.0  71.0405.0 = A2-11
38.20-38.60  rings  2.5 2.5 00 
71.0455.7  2 oil holes
’51-55  F.B.M. P48, P3 (3 Marce)
’56-65? Minarelli P1P3, P4
69-80  Minarelli V1 (some), ’76-80 V1 (1hp US)
12-22-16-38.00-0 37.93 $65.0 71.0405.0 0 4500  Asso 825
12-22-16-38.40-0 38.34 $65.0 71.0455.7/2 4520  Asso 771
12-22-16-38.60-0 38.54 $35.0 71.0455.7/3 4530  no rings!

38.00 12+22+15.5+3.5=53.0  71.0404.0   
38.20-38.60  rings  1.5 1.5 00  71.0454.7  2 oil holes
’65?-70? Minarelli P3 (3 Marce)
use 71.0405.0

38.80 12+22+15.5+4.0=53.5  71.0409.0 = A24-31
39.00-39.80  rings  1.5 1.5 00  71.0459.7  no oil holes
’69-79 Minarelli V1, V1N
12-22-16-39.00-N 38.95  $60 71.0459.7/1 says 39
superseded to 71.0410.0 

38.80 12+22+15.5+4.0=53.5  71.0410.0 
39.00-39.80  rings  1.5 1.5 00  71.0460.7  2 oil holes
’80-86+ Minarelli V1P 
’73?-78? P3S, W3-QM, ’75?-82? G1, G1R
’69-75+ P4E Export, P6E Export, 70’s engine case
12-22-16-38.80-0 38.72  none  71.0410.0  0 4540  62.0115.0
12-22-16-39.00-0 38.92  $73.0 71.0460.7/1 4550 Asso 1641
12-22-16-39.20-0 39.12  none  71.0460.7/2 4570 Asso 1641

12-22-16-39.40-0 39.32  $73.0 71.0460.7/3 4570 Asso 1641

12-22-16-38.80-G 38.72 
none  GOL 0034

38.70 12+22+15.5+4.0=53.5  71.0406.0 
’79 and some ’78 Min. V1 piston port, (USA only)
’80-85+ Minarelli V1P piston port, (USA only)
12-22-16-38.70-0 38.62  n.a. 71.0406.0  0 Asso 1641

41.00 12+22+18.0+2.0=54.0  71.0426.0 = A42-222
41.20-41.60  rings  L2  1.5 00  71.476.7  
’70-75+ Minarelli P4-55      

12-22-18-41.00-0 40.9x  n.a. 00.1111/0 Asso 1989
12-22-18-41.20-0 41.1x  n.a.  
12-22-18-41.00-G 40.9x  n.a. GOL 0529

42.00 12+22+18.0+2.0=54.0
42.20-42.60  rings  1.5 1.5   
’75-80+ V1-60 on Carabela 60
12-22-18-42.00-0 40.9x  n.a. 00.1111/0 says 42
12-22-18-42.20-0 41.1x  n.a.  

45.00 12+22+18.0+2.0=54.0
45.20-45.60  rings  1.5 1.5 00  71.0485.7
’75-80
V1-70 Commercial (low-rpm use)
12-22-18-45.00-0 44.93  n.a. 71.0435.0?  Asso 1983
12-22-18-45.40-0 45.33  $70 71.0485.7/2 in box

 

2. For stroke 42, iron sleeved alum. cylinder, piston port

38.80 12+22+15.0+0.0=49.0  71.0413.0 = A42-102 
39.00-39.60  rings  L2  1.5 00  71.0463.7  2 oil holes, flat top
’70?-75? P4E Export, P4-CS Compact System
’70?-75? P6R Radiale

12-22-15-38.80-0 38.72  n.a. 71.0413.0  0  62.0118.0
12-22-15-38.80-G 38.7x  n.a. GOL 0029 for P4
12-22-15-38.80-G 38.7x  n.a. GOL 0030 for P6

38.80 12+22+13.5+0.0=47.5  71.0412.0 = A42-102 
39.00-39.60  rings  L2  1.5 00  71.0462.7  2 oil holes, flat top
’70?-75?
12-22-13-38.80-0 38.74  $65 71.0412.0

12-22-13-39.00-0 38.94  n.a. 71.0462.7/1

 

3. stroke 42, all-aluminum cylinder, piston port

38.80 12+22+15.5+4.0=53.0  71.0408.0  
38.00-38.00  rings  1.5 1.5 00  —
’78?-86? Minarelli V1H 

38.8 12+22+15.5+4.5=54.0  71.0422.0  
39.00-39.60  rings  L2  1.5 00 
’70?-75? P6R Radiale, ’74?-78? P6 Sport 
12-22-15-38.80-0 38.72  n.a. 71.0422.0  0  62.0127.0
49.6cc  rings c1.5n  c1.5n

12-22-15-38.80-S 38.72  n.a. GOL 0028A

In the 1980’s most manufacturers changed from piston port intake to reed valve intake.

 

4. stroke 39, all-iron cylinder, case reed valve intake

40.30 12+22+15.0+2.0=51.0  71.1202.0 
40.60-40.80  rings  L2  1.5 00  71.1602.7
’81-90+ Minarelli V1L, ’87-90 V1L (US)
12-22-15-40.30-L  40.2x  n.a. 71.0000.0/0 4541  62.0145.0

 

5. stroke 39, iron-sleeved aluminum cylinder

40.30 12+22+15.0+2.0=51.0
40.60-40.80  rings  1.5 1.5 00  71.1602.7
’85-87   Minarelli V1H (piston port intake)
’87-90+ V1HL, V1HLE (case reed valve intake)  

12-22-15-40.30-H 40.2x  n.a. 71.0000.0/0 4543  62.0400.0
12-22-15-40.60-H 40.5x  n.a. 71.1602.7/1 4553=4551
12-22-15-40.80-H 40.7x  n.a. 71.1602.7/2 4563=4561

 


12-22  

38.0 – 38.6 for ’56-64   Morini F48, 3M,
’68-79+ Morini S5K, S5K2
rings c2.0n c2.0n  length 12+22+15.5+5.5=55.0
pin up  lo bore M#  skirt  price  Morini#

12-22-16-38.00-1 37.93  n.a. 23-0101 says Asso 771
12-22-16-38.20-1 38.1x  n.a. 23-0102
12-22-16-38.40-1 38.3x  n.a. 23-0103
rings c2.5n c2.5n  length 12+22+16.5+4.5=55.0

pin up  lo bore M#  skirt  price  GOL#
12-22-16-38.00-G 37.93  $60 GOL 0027 38.0
12-22-16-38.20-G 38.1x  n.a. GOL 0027 38.2
12-22-16-38.40-G 38.3x  n.a. GOL 0027 38.4
12-22-16-38.60-G 38.5x  n.a. GOL 0027 38.6

12-22

39.0 – 39.6 for ’64-68+ Morini 3CV
rings c2.5n c2.5n  length 12+22+16.5+4.5=55.0

pin up  lo bore M#  skirt  price  GOL# Malanca
12-22-16-39.00-A 38.9x  n.a. GOL 0027A 38.0
12-22-16-39.20-A 39.1x  n.a. GOL 0027A 38.2
12-22-16-39.40-A 39.3x  n.a. GOL 0027A 38.4
12-22-16-39.60-A 39.5x  n.a. GOL 0027A 38.6

12-22

39.0 for ’78-80+ Morini S5E (iron cylinder)
rings L2.0  c2.0i   length 12+22+15.0+3.5=52.5

pin up  lo bore M#  skirt  price  rings L2.0  c1.5n

12-22-15-39.00-0 38.94  $70 23-0133 Asso 1386
12-22-15-39.00-G 38.9x  n.a. GOL 0036S 39.0
12-22-15-39.20-G 39.1x  n.a. GOL 0036S 39.2
12-22-15-39.40-G 39.3x  n.a. GOL 0036S 39.4

more oversizes up to 40.4

12-22 

39.0 for 1981-82 Morini S5N (all-aluminum cylinder)
39.0 for 83-86?   Morini S5T (all-alum. cyl. reed valve)
39.0 for 86?-90+ Morini S5GS (all-alu. cyl. reed valve)
pin up  lo bore M#  skirt  maker  price  rings

39.0 for 1990’s? Morini S6E (all-alum. cylinder)
pin up  lo bore M#  skirt  maker  price  rings

Big Bore Pistons
pin up  lo bore M#  skirt  ring1 ring2  maker  price    46.0 bore, 12 pin, 21.5 upper
12-22-15-46.00-0 45.93 L2.0n c1.5i  Asso    $70 23-0140 Morini 70cc, says Asso W 2508 
pin up  lo bore M#  skirt  ring1 ring2  maker  price    47.1 bore, 12 pin, 22.5 upper

12-22-15-47.10-0 47.03 L2.0n c1.5i  Asso    $70 23-01?? Morini 70cc AW 2666, AA on top

 


12-22  
                               left, Demm, right, Minarelli V1

38.8 for ’77-80+ Demm Smily 
pin up  lo bore M#  skirt   maker  price  rings L2.0   c2.0n
12-22-16-38.80-2 38.73  Asso    $65 4540HP fits Minarelli

 


12-22

38.8 – 39.4 for ’65 Harley Davidson M50
pin up  lo bore M#  skirt   price  rings c1.5i  c1.5i
12-22-16-38.80-H 38.7x   n.a.  22028-65P
12-22-16-39.00-H 38.9x   n.a.  22029-65P
12-22-16-39.20-H 39.1x   n.a.  22030-65P
12-22-16-39.40-H 39.3x   n.a.  22031-65P

pin up  lo bore M#  skirt   price  rings c1.5n  c1.5n
12-22-16-38.80-0 38.72  $75 71.0410.0  0 Minarelli substitute
12-22-16-39.00-0 38.92  $73 71.0460.7/2 Minarelli substitute
12-22-16-39.40-0 39.32  $75 71.0460.7/6 Minarelli substitute

 


12-22

40.0 for ’83-86+ Garelli Monza GT
pin up  lo bore M#  skirt  price  rings L2.0  c1.5n
12-22-16-40.00-0 39.9x  n.a. 208703.2.150

 



Casal 40mm piston top

Ø40 top

Casal 40mm piston bottom

says 401

12-23 pistons for Casal M140 engine on K177, Zundapp?

pin up  lo bore M#  skirt  ring1 ring2  maker  price    40.0 bore, 12 pin, 23 upper
12-23-16-39.98-D 39.96 c2.0n c2.0n Mahle  $70 Casal alum cyl 39.98 D  Mahle 401
12-23-16-39.99-E 39.97 c2.0n c2.0n Mahle  n.a. Casal alum cyl 39.99 E  Mahle 401
12-23-16-40.00-F 39.98 c2.0n c2.0n Mahle  n.a. Casal alum cyl 40.00 F  Mahle 401

Casal Ø48 Piston top

Ø48 top

Casal Ø48 piston bottom

says 481

pin up  lo bore M#  skirt  ring1 ring2  maker  price    48.0 bore, 12 pin, 23 upper
12-23-16-47.98-D 47.96 c2.0n c2.0n Mahle  n.a. Casal alum cyl 47.98 D  Mahle 481

12-23-16-47.99-E 47.97 c2.0n c2.0n Mahle  n.a. Casal alum cyl 47.99 E  Mahle 481
12-23-16-48.00-F 47.98 c2.0n c2.0n Mahle  n.a. Casal alum cyl 48.00 F  Mahle 481

Casal (made in Portugal) pistons are made in Germany by Mahle. They say “saida” on top, exhaust side, Portuguese for “outlet”.

Casal pistons 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 c2.0n (FG gap style), like Garelli. 

 



13-13.5

42.0 – 42.25 for 78-81 Indian AMI-50
pin up  lo bore M#  skirt  xxxxooo  price  part#
13-14-14-42.00-0 41.96 bare xxx  $48 E650-00-50
13-14-14-42.00-1 41.96
complete none  6131 std
13-14-14-42.25-0 42.21 bare xxx  $48 E650-10-50
13-14-14-42.25-1 42.21 complete none  6132 1os

42.0 – 42.25 for 70-77 Honda PC50K1
pin up  lo bore M#  skirt  xxxxooo  price  part#
13-14-14-42.00-0 41.96 bare xxx  $48 13101-081-000
13-14-14-42.00-1 41.96
complete none  6131 std
13-14-14-42.25-0 42.21 bare xxx  $48 13102-081-000
13-14-14-42.25-1 42.21 complete none  6132 1os

 



13-15.5

39.0 for ’57-64 Ward Riverside (4 models)
AV7 Dbe, AV7 V, AV7 V2 engines, all-al. cyl.  rings c2.0n  c2.0n
pin up  lo M# bore  skirt price maker  part#
13-15-22-R   39.00 38.99 n.a. MB 14819 

39.0 for ’74 to 6/76 Motobecane 40, 50, 50V
AV7 Db, AV7 Vb engines, all-alum. cylinder  rings c2.0n  c2.0n
pin up  lo M# bore  skirt price maker  part#
13-15-22-A   38.95 38.94 n.a. MB 21240 sort A
13-15-22-C   38.96 38.95 n.a. MB 21242 sort C
13-15-22-E   38.97 38.96 n.a. MB 21244 sort E
13-15-22-G  38.98 38.97 n.a. MB 21246 sort G
13-15-22-J   38.99 38.98 n.a. MB 21248 sort J
13-15-22-L   39.00 38.99 n.a. MB 21250 sort L
13-15-22-N  39.01 39.00 n.a. MB 21252 sort N
13-15-22-P   39.02 39.01 n.a. MB 21254 sort P

39.0 for 6/76 to 1980 Motobecane 7, 40, 50, 50V
AV7 Dc, AV7 Vc engines, all-alum. cylinder  rings c2.0i  c2.0i

pin up  lo M# bore  skirt  price  maker  part#
13-15-22-W  38.93 38.92 $70 MB 22273 sort W
13-15-22-AA 38.94 38.93 $70 MB 22274 sort AA
13-15-22-A   38.95 38.94 $70 MB 22275 sort A
13-15-22-C   38.96 38.95 n.a. MB 22276 sort C
13-15-22-E   38.97 38.96 $75 MB 22277 sort E
13-15-22-G  38.98 38.97 n.a. MB 22278 sort G
13-15-22-J   38.99 38.98 n.a. MB 22279 sort J
13-15-22-L   39.00 38.99 n.a. MB 22280 sort L
13-15-22-N  39.01 39.00 $75 MB 22281 sort N
13-15-22-P   39.02 39.01 $75 ΘB 22435 sort P  says P
13-15-22-O  39.12 39.11 $75 ΘB 22435a oversize 

piston-cylinder clearance 0.005-0.010 mm (0.0002-0.0004″), maximum 0.05 mm (0.002″)
ring gap 0.10 – 0.20 mm (0.004-0.008″), maximum 0.40 mm (0.016″)

 

 



14-18 Jawa USA

39.0 for Jawa 210?
pin up  lo bore M# skirt  price maker  part#  rings L2.0  none
14-18-15-39.00-0
38.94 n.a. Meteor

39.03 for ’70-83 Jawa 207 (Babetta)
pin up  lo bore M# skirt
  price maker  part#  rings c2.0i   c2.0i

14-18-15-39.02-0 38.97 n.a. Jawa 281218A   says   A Y
14-18-15-39.03-0 38.98 n.a. Jawa 281218B   says   B Y
14-18-15-39.04-0 38.99 n.a. Jawa 281218C   says   C Y
14-18-15-39.27-0 39.22 n.a. Jawa 281218/1A says 1A Y
14-18-15-39.28-0 39.23 $60 Jawa 281218/1B says 1B Y
14-18-15-39.29-0 39.24 n.a. Jawa 281218/1C says 1C Y
14-18-15-39.52-0 39.47 n.a. Jawa 281218/2A says 2A Y
14-18-15-39.53-0 39.48 n.a. Jawa 281218/2B says 2B Y
14-18-15-39.54-0 39.49
n.a. Jawa 281218/2C, says 2C Y
14-18-15-39.77-0 39.72 n.a. Jawa 281218/3A says 3A Y
14-18-15-39.78-0 39.73 n.a. Jawa 281218/3B says 3B Y
14-18-15-39.79-0 39.74 n.a. Jawa 281218/3C says 3C Y

14-18-15-40.02-0 39.97 n.a. Jawa 281218/4A says 4A X
14-18-15-40.03-0 39.98 $65 Jawa 281218/4B says 4B X
14-18-15-40.04-0 39.99 n.a. Jawa 281218/4C says 4C X

Jawa original pistons were sold with rings, but without pin or clips.

Jawa Pistons

 Size translation: The table says a “1B” piston is 39.21 mm, measured “34,5mm from the base” just below the lower ring. Four “1B” 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, and 0.02 more at the skirt. Other samples 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, all 0.02 wider at the skirt. 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. Jawa piston sizes (measured at the lower ring) are, on average, 0.02 mm less than standard piston sizes (measured at the skirt).

Piston to cylinder clearance: From the Puch service manual the piston to cylinder clearance for a similar steel sleeved aluminum cylinder, is min 0.030, max 0.055 mm. 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. Subtracting 0.02 mm from this gives min 0.045, max 0.055, more in agreement with Puch. 

 

 



14-21 Jawa USA

38.0 for Jawa 50-3 on 1969 Indian Boy Racer (50mph)
pin up  lo bore M#  skirt  ring1 ring2  maker  price
14-21-19-38.00-0 39.92 c2.0i c2.0i c2.0i Jawa none

This has 3 rings 38.0 x 2.0 with GI gaps.

Total length 57, crown 3, side length 57 – 3 = 50.0

 

 



14-24

40.0 for 1977 Flandria Bermuda
pin up  lo bore M#  skirt  ring1 ring2  maker  price
14-24-12-40.00-0 39.9x c1.5n c1.5n Fland. n.a.

This is unusual in many ways. The transfer flows through the piston instead of around it. The wrist pin is lowered to allow more intake air flow. This upper length of 24 is the most for 50cc pistons. The wrist pin measures 13.98 x 33 mm.

 

 

 

 

100’s more vintage replacement pistons of all sizes are in the GOL Pistons Vintage Catalog, a pdf download.