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Solex 3800 USA by BrianSolex

Solex S 3800 USA specifications & tech. info

Solex S 3800 USA specifications & tech. info:


- these specifications are for the Solex S 3800 USA


Engine Size:


 49 cc


Fuel Mixture / Mix / Ratio / Proportion:

- 2.5% or 40:1  

- Mix three (3) ounces of high-quality two-stroke oil with one (1) gallon of regular unleaded gasoline/petrol. 

- use Regular Unleaded gasoline/petrol, 87 Octane.

- Disregard the fuel mixture information in the handbooks as it is outdated.

*  NEVER add oil directly to the Solex fuel tank.

*  Mix your fuel in a clean, separate container. 

- I recommend Lucas semi-synthetic or Castrol 2T two-stroke (two-cycle) engine oil.

- a shot glass or a 35 mm film canister can be used to measure one ounce.



Spark Plug:


Champion       L86C

Bosch            W7AC

NGK               B6HS

Denso            W16FS-U

AC                 44 L, 45 L

Motorcraft       AE32

Autolite           2656

Marchal          V36A 

XLG                FF 70 Y 

Cyklon            43

Flashpoint       FP5CR


Spark Plug gap:


0.020" (0.5 mm)


(CDI ignition - 0.6 mm) 



Piston Ring end gap:


minimum - 0.006" (0.15 mm)

maximum - 0.012" (0.3 mm)



Tire/Tyre pressure:


Front and Rear:

    2 Bar

    30 psi



Tire/Tyre size:


Front & Rear:


  19" x 1 3/4"



Tire/Tyre type:


  Cyclomoteur Type Y straight tread


Pedal thread:


1966-74 S 3800 USA (made in France) - M14 x 1.25

1999-2006 S 3800 USA (made in Hungary) - 9/16" - 20





  0.8 hp



Maximum Power: 


  585 Watts ( 0.58 kw) @ 2,500 rpm



Top speed:


  18.7 mph   (30.1 km/h) 



Electrical System Voltage:


  6 Volts







1966 - 74 S 3800 USA & S 3800 DOT headlight bulb: 6 Volt 6 Watt 1 Amp, E 10 base (yellow or clear)


1967-74 California 3800-S sealed-beam headlight bulb: CEV #125, 6 Volt 21 Watt 


1999 - 2006 Hungarian S 3800 headlight bulb: 6 Volt 15 Watt, P26S base (clear)




1966 - 74 S 3800 USA taillight bulb: 14 Volt AR*, E 10 base


1966 - 70 S 3800 DOT, MALY unit :   2 x 14 Volt AR* (taillight & brake light)


1967 - 74 California 3800-S, CEV unit:  #1154, dual element, 6 Volt


*note: 14 Volt AR = 14 Volt 7 Watt    (can use 12 Volt 6 Watt, or 6 Volt 1.8 Watt)







  61 - 62 lbs. 



Wiring Diagrams / Lighting:


1973-74 S 3800 USA wiring diagram   



Yellow - main power from stator to switch paddle

              (power for the lighting exits the stator via the serrated stud; there is no wire connection

               between the serrated stud and the switch. The switch paddle must contact the serrated

               stud when the switch lever is turned CCW.)

Red - power from headlight switch paddle, through spring

           and bronze strip, to headlight.

Blue - power from bronze strip to taillight wire

Green - ground (wire from headlight to fuel pump screw)


*Note: the 1966-72 S 3800 USA (and the S 3300) is similar, but instead of a ground wire,

           there is a ground tab mounted on the front of the fuel pump.

           The tip of the bulb must touch the ground tab. See photo below:



                                                                  above: 1966-72 headlight ground tab



                                                                           Taillight wire connection: 


                                                                 Taillight wire connection

                                            ~ the connector on the end of the taillight wire attaches to

                                                the bronze strip at the rear of the plastic engine hood. 


                         For additonal info and photos, see:




      MALY brake light switch

     - used on Solex S 3800 DOT and Solex California 3800-S

004 a                                                             MALY brake light switch wiring

                                                            - switch is normally closed, held open  

                                                            - chain is attached to rear brake cable 

                                                            - when brake cable moves forward, switch closes,

                                                              allowing power to brake light (stop light)


MALY-light a          

                                             above - MALY taillight assembly

                                                       - used on Solex S 3800 DOT





1999-2006 Hungarian S 3800 USA wiring diagram:

3800 wiring diagram Hungarian +




Stator / Magneto:


012 b


A - Ignition Coil

B - Lighting Coil

   * Coils may be different colors than shown. 

C - Condenser

D - Points adjusting screw

E - Lock Screws

F - Points (Contacts)

G - Rupture Mark

H - Ignition Coil - Points connection

I  - Cam Wiper Pad

J - coil fixing screws, M4 - 0.7; length 22 mm

K - Lighting Coil connection 


 ~ Flywheel Puller

          - Do not use a standard two - , three - , or four - jaw puller to remove the flywheel (rotor).

          - Use a puller that makes use of the three M6 tapped holes in the flywheel (rotor).

          -  http://briansolex.free.fr/toolkit.html


~Ignition Points / Points Gap:

 The ignition points must be adjusted so that they just begin to open when the "RUPTURE" marks on the flywheel (rotor) and engine (G in above photo) line up, rotating the flywheel (rotor) clockwise.

There is no set points gap on a Solex engine.

The amount that the points open is not relevant.    




      Instructions for installing Hungarian electronic ignition kit:


Hungarian cdi instructions





Parts of the carburetor


006 a

A - air jet

B - fuel filter

C - START lever (air choke lever)

D - fuel Jet

E - fuel return spout

F - throttle barrel

G - cable lock screw

H - cable pulley

 I  - throttle lever

J - return spring

K - cable sheath abutment bracket

L - air horn (venturi)


How to replace the carburetor fuel filter:



Fuel Tank


How to Replace the fuel tank fuel filter:





Rear Wheel Hub

(approx. 1967 to 1974 ... 83 mm drum)


rear hub 74 b


How to remove / install the rear brakes:



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  How to Date a Velosolex Solex S 3800 USA

 (How to Determine Year of Manufacture)




Engine Serial Numbers:

40xxxxx - 45xxxxx       1967-68

500xxxx - 503xxxx       1967

504xxxx - 514xxxx       1968

515xxxx - 5198xxx       1969

5199xxx - 523xxxx       1970

524xxxx - 52717xx       1971

52718xx - 5277xxx       1972

528xxxx - 5305xxx       1973

5306xxx - 532xxxx       1974

532xxxx - 534xxxx       1974-78 


Frame Serial Numbers:

  1970:  800xxxx - 800xxxx 

  1971:  800xxxx - 801xxxx 

  1972:  801xxxx - 802xxxx    

  1973:  801xxxx - 804xxxx 

  1974:  803xxxx - 807xxxx 


Note: Engine numbers, not frame numbers, are used to determine the year of manufacture of a Solex. 



Please contact me for help in determining

the year of manufacture of your Solex S 3800 :    

e-mail BrianSolex : Velosolex3800@aol.com



~ The 14-3-1966 (or 25-10-1962) date that is cast into the top of the crankcase is not the date of manufacture;

It is the date of approval of the Cyclomoteur 3800 engine (or Cyclomoteur 2200 engine). This same date is cast into the top of every Cyclomoteur 3800 engine.  


 ~ The Cyclomteur 3800 engine was used not only on the S 3800,

     but also on the model 5000, the model 4600, and the Micron.


 ~ The online Solex engine serial number charts do not pertain to Solexes sold new in the USA.


How to Find the Engine Serial number and the Frame Serial number on a Solex S 3800 USA:


Please contact me for help in determining year, model or version of your Solex:




      S 3800 USA - No Spark:

1. Install a NEW spark plug...not almost new, good as new, only used once, etc. NEW, NEW, NEW. Be sure to use a gauge and set the electrode gap to 0.5 mm

*Check for spark by carefully holding the threaded portion of spark plug against the cylinder head or crankcase and spinning the flywheel clockwise, looking and listening for a blue / white / purple spark to crack across the spark plug gap. 

 See video: http://www.youtube.com/watch?v=MevTYVxWnd8

~ An orange / yellow spark is no good.

~ Feeling a jolt while holding the end of the spark plug wire means nothing

2. still no spark...install a new spark plug wire. Be sure that the end of the spark plug wire has a good clean connection against the tab on the back of the ignition coil.

 Check for spark as above*.

3. still no spark...remove flywheel (rotor) using special Solex flywheel puller; clean the points (search online for instructions on cleaning points). Disconnect the ignition coil from the points and test the points for continuity when closed, no continuity when open. Reconnect the ignition coil wire. Install flywheel. Adjust the points as described above in the Stator / Magneto section under ~Ignition Points / Points Gap. Check for spark*.

4. still no spark...install new condenser, check for spark*

5. still no spark...install new ignition coil, check for spark*

6....install new flywheel.

(On a Solex, the flywheel key is part of the flywheel casting. The key fits into the keyway slot on the crankshaft to correctly position the flywheel on the crankshaft. You must verify that the flywheel key has not been sheared off.)


Instructions for making a simple Solex flywheel puller (magneto rotor extractor) can be found on this page:



For instructions on how to test a condenser, see this page:



BrianSolex e-mail: Velosolex3800@aol.com





Value / Worth / Price / Prices of a Velosolex Solex moped bike


What Is the value of a Velosolex Solex bike?

What is a Velosolex Solex bike worth?

   There are no set prices for Velosolex Solex bikes.


 Prices can be affected by time of year, bike location, and whether or not the seller is willing to pack and ship the bike.

time of year - prices are generally lower in Fall and Winter.

location - Solexes were not sold in every State...most were sold in Michigan, Ohio and Indiana, so the prices are lower in that area.

pack and ship - if you are only able to sell locally, the prices will be lower.


   Listed selling prices do not determine the value or worth i.e. just because you see a Solex with a listed price of $1,000, this does not mean that this is the value or worth, or that this is what the bike will sell for.  It is just showing what the seller thinks the bike is worth.





To contact BrianSolex...e-mail: Velosolex3800@aol.com


I'm happy to answer any technical or historical Solex questions that you might have.














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