FAQ  (Frequently Asked Questions)

In this part you may probably find answers to your questions.
Remind well, that the majority of the published questions will be technology-related and there will be just a few general questions.
At the start of this renewed website the number of items was limited, but will increase in due time. It depends on you.
We won't answer simple questions, for those questions: please, visit one of the club websites or forums under main button 'Links'.

  • Ignition system
  • Why not an electronic ignition system?
  • Why do my bulbs blow?
  • Dismantling Dimoby clutch
  • Cleaning carburetor and needle jet
  • Tuning / more speed
  • Tyres for 21 inch rims.
  • Taps for mobylette.
  • Sprocket for SP93, AV92 and SP94TT
  • M5x0.9, M3x0.6 and M10x1 ??? French thread?

  • Why English as main language?
  • Why is this website so fast on smart phones?
  • Can I get any part with help of Pantin?
  • What can Pantin do for me?
  • Where can I find files to print mobylette parts by myself?

  • NEW!
  • Critical success factors for long rides in France.

  • Module: Failure Analysis.

  • Whenever your question is different: please, contact us by email.


    In the past most questions concerned ignition.
    We are delighted to say: Problem solved! In the past 20 years Pantin has done a lot to promote the conversion from old internal coils to external coils.
    From 2006 we have promoted the use of external capacitors, too.
    Several publications saw the daylight and recently an extended version in Dutch was published. Perhaps an English translation will be made, when we are getting bored....
    Most questions about ignition can be find in the ignition manuals under Technical Publication

    Nevertheless we will give here a summery of the problem:
    Many internal high tension coils show the same problem: they are just worn. Even brand new coils (NOS), which never have been used show the same problem: the insulation properties of the thin windings of the coil have become quit poor. As a result of the high tension in these windings - about 15.000 Volts -there will be a lot of short circuits. The spark becomes very weak. The signs are often like this:

  • Starting can give a lot of trouble.

  • After 5 minutes, when the coil is getting warmer and the resistance of the copper windings has increased, ignition fails.
    Remind that the pressure of the mixture in a hot cylinder is higher and the spark meets more resistance.

  • Sometimes the engine runs fairly well, but doesn't reach its top speed.
    Anyway a common problem, but an affordable solution is shown in the publications that doesn't interfere with the authentic looks of the old timers.

  • Coil and capacitor hidden in front of the rear mud guard.


    People often ask why we don't apply electronic ignition systems, though there are sets for the AV7-engine available?
    Well, there several reasons why we don't:
  • The flywheel should be replaced by a smaller one. This will spoil the authentic looks!
  • Modern electronics are not always reliable; in a hot environment electronic parts are vulnerable!
  • Modern electronics cannot be repaired easily when you are in the middle of nowhere.
  • The steel core of the former high tension coil can be used to make a feeding coil. Thus we never meet fitting problems.


    The trouble mostly starts with the lighting coil that offers a current with a high tension of 40 Volts.
    This happens when there is no or a low load. When there is normal load of a front and rear light, the voltage will decrease rapidly.
    Three important reasons why bulbs will blow:

    1. You are using bulbs designed for a bicycle.
    2. A bad connection at the bulbs or switch.
    3. A single brake bulb or flashing indicator will not decrease your current voltage sufficiently.

    What van be done regarding these problems?

    Ad1. Apply the right bulbs with prescribed power (Watt).
    The more power the bulbs will use; the lower the voltage in the circuit will be.
    A mobylette with an 8 Watt electrical system, requires bulbs with a total power of at least 10 Watt.

    Ad2. Check your wires and mass cables. Remove oxidation at the connectors and bulbs. Consider the use of contact spray.
    A bad connection at one of the bulbs or switch lowers the total bulb power and the tension becomes automatically too high.

    Ad3. Mount a zener diode that will stabilise your tension in the circuit.
    For a brake system or in case of flashing indicators this is a good solution.

    The zener diode on the right side (red arrow) protects a bulb in the tail light,
    which will light when the brake is used. In the electrical circuit the zener diode is mounted behind the brake switch, so normally it does not waste energy. Just when the bulb is activated, this zener diode will limit the tension to 6 Volt.

    Modern zener for brake circuit

    A lot of space at the AV92/SP93


    Dimoby coupling From time to time an experienced mechanic is calling, because he is not able to dismount the centrifugal clutch.
    Let us see how we can fix it.

    Firstly you remove the hexagon nut and the grease nipple. Next you need an extractor, which has to be screwed into the cover of the clutch. An inner bolt pulls the cover off the camshaft. If you cannot find an extractor contact me. When you look at the drawing , you will see in front of and behind the red ring a so called "Seeger ring or circlip ring ". Mostly people manage to remove the first ring and think that the job has done. They are looking against the (in this drawing =  red colored)  washer, which covers the second circlip (Seeger) ring, and they are very surprised that they cannot remove the coupling housing. The red washer has to be removed with a magnetic extractor or with two small pins. Because of the grease this simple ring has been stuck on the second Seeger ring. Sometimes it helps when you shake the engine a bit.
    After the washer has been taken away, the second Seeger ring can be dismounted quite easily.

    Detail of Dimoby centrifugal clutch.

    The red washer has to be removed off the camshaft before you can see the second circlip ring.

    Dismantling Dimoby clutch


    Carburetors can be very polluted.
    Most people are aware of that fact and will clean the carburetor thoroughly.
    However, often they forget to check the little hole of the needle jet. This hole provides the mixture with some extra petrol when the throttle is nearly closed.

    When your engine has stationary problems this may be the cause.
    For the 12 mm carburetors and higher you must dismantle the needle jet at the underside of the carburetor as shown in the picture on the right.

    For older models (without needle jetholder) the needle jet must be removed and inserted top-down via the throttle valve bore.

    Some carburettors like the ones for BG and early AV42 have a threaded needle jet, so with a socket wrench it has to be removed.

    Examples of jets for a 12mm carburettor

    threaded jet

    Example of a threaded needle jet

    By coincidence we found a lot of different jets a long time ago. We still wonder about the great differences in geometry.
    The one in the middle proved to be excellent in a 12 mm carburettor.

    Some examples of needle jets with holes for stationary speed.



    Our mission is not to ruin ancient engines by increasing their performance, but getting them on the road again according their original specifications.
    Though they are old now, they should run like in their young days or even better, when improved sealing, ignition or lubrication additives have been applied.
    Unfortunately many people complain that their engine is not running well after they have restored that engine "perfectly". The reality is - without any doubt - different. We always note many mechanical defects in vehicles. Transmissions malfunctioning because of worn chains, sprockets, chain wheels and bearings. Crankshafts, pistons and cylinders with too much clearance.
    Ignition is an other source of failure. If the spark fails regularly then the performance is considerable lower.

    The best and cheapest start for power enhancing is: make sure that the basics are good.
    - All parts should be in a "pretty" mechanical condition.
    - Strong ignition system.
    - A cylinder with Nicasil lining as manufactured by Airsal .
    - Better lubrication by using oil enhancing additives as TSL or Triboron.

    TSL: a great oil enhancer

    If so, then you can start thinking about improvements. Mostly your little bike will run fast enough now. It's design was not meant for high speeds. Frame, brakes, tyres and suspension are inadequate for use at high speeds.
    The famous French poet La Fontaine used to say: "Do not hurry, but leave on time!" We only can agree with that statement.

    Top 10 of problems that influence factory speed

  • Pre-ignition is wrong
  • Poor ignition coil
  • Poor capacitor
  • Spark plug failure
  • Diffuser in carburettor is too large or too small
  • Piston rings too tight (play should be 0.2 mm)
  • Worn piston and piston rings
  • Gas throttle cannot be opened totally
  • Leakage of crankshaft seals
  • Exhaust is silt (AV92 and SP93)
  • Transmission problem (coupling, brakes too tight, chain)


    Several years ago these tyres were a problem, but suddenly some manufacturers started to produce these tyres again.
    There are several tyres fitting on the same 21 inch rim:

    • 600 x 50 B     Chambrier (F)
    • 25 x 2            At jumbles in the Netherlands or Belgium.
    • 24 x 1.5 x 2   Motorrijwielhandel van Gestel in Eindhoven and Pebro-wheels Meijel both in The Netherlands.


    A large number of different taps can be found on mobylette. Some are availabele from stock, while others cannot be repaired ; at least they say so.
    At Pantin we are able to fix those taps. In chapter Creations - Parts-overhauled we show some solutions.


    A hard to get sprocket and especially when you want to apply a small one (12 and 13 teeth).
    Since we prefer small ones, we had to make those by ourselves.

  • At the old worn sprocket all teeth will be removed by way of grinding.

  • The very hard sprocket has to be annealed in a fire of about 800 degrees Celsius.

  • The sprocket will get its definitive core diameter on a lathe.

  • A flat annealed sprocket will get a new bore, corresponding the hub of the machined old sprocket. A special collet is needed to guarantee the concentricity.

  • Both parts will be welded to one piece.

  • The teeth must be hardened and tempered for long life quality.

  • If you want such a small sprocket do not ask us, but consult a professional company. We just like prototyping.
    On the right you see a sprocket with 12 teeth, which is ready to be welded.


    Special sprocket


    Everybody who wants to repair a mobylette will meet this problem: normal metric bolts and nuts will not fit. It is not a matter of strange French thread, but it is just metric thread with a different pitch. The well-known screws for the engine side panels are an example. They choose a long time ago not for standard M5x0.8 but instead of this for M5x0.9 (mm).
    Why did they not choose for standard thread?
    The only reason is a commercial one; as customer you cannot apply a cheap standard bolt or nut.
    The fact that Motobécane often used bolts and nuts with a pitch of 1mm, is an advantage when you make the thread on a lathe. You do not have to change the pitch every time. We found a pitch of 1mm at next threads: M7, M8, M10, M11, M12, M13, M14, M24, M26 and M46. This list, however, is not exhaustive. Happily most taps and dies can be found on the net.


    This website will focus on technology for people all over the world. We will not exclude a lot of interested people for just a few that cannot understand English. Besides www.translate.google.com translates English to Spanish and French better than from Dutch to other languages.


    Actually this website was not special designed for smart phones, in spite of the fact that many visitors are using a smart phone for web browsing.
    We simply love clean code and keep our images small. This website is less than about 15MB!; just 3 high resolution images of a camera.


    There is no such list, where you can order parts at Pantin. Nevertheless we are involved in many mobylette restoration projects.
    Our stock of spares is limited and meant for our own projects and to help people with their projects. Sending an email is the best way to contact us. If you are a real - mobylette enthousiast - we may give you some support.


    If a part is absolutely not available anymore then a study at Pantin may be started.
    It does not depend on later revenues, but on the question: how intriguing is the problem? Can the problem become a real challenge? Being a hobby we can afford to do that kind of studies, without a boss daily inquiring about the progress.

    Some examples:

  • In the Netherlands you cannot find yellow plates anymore. Those used to be compulsory for mopeds on the front mudguard.
    We started a project and designed several plates.

  • Some tools were not available; so we have made a small batch of several tools.

  • Capacitors (except Bosch) are often not very reliable; renewing the electrical ignition system was a nightmare for many owners.
    We made it more transparent and easier to fix by all kind of smart improvements. Basic findings have been published under Publication on this site.

  • Recently we have started a study about a Kaptein tank cap with the nice Kaptein logo on top of it. This cap should be petrol resistant and that is why we only apply stainless steel, nylon and viton.
    In spite of the complicated shapes we are very pleased with the results of our stainless steel prints as well as the flexible nylon ones.


    Public sharing of files for 3D prints and public sharing of specific process information is not our policy.
    Nevertheless we cooperate a lot with friends and third parties; exchanging special information is part of it. When you want to design a special part and you need some help, you should ask us.


    Failing is positive, when it leads to improvements.

    Some years ago during a trip to the south of France, we had chosen for the most basic way: riding on a mobylette and sleeping in a tent at a camping site.
    This choice will always lead to an extra burden for your mobylette.
    In spite of all preparations we had to cancel this trip for several reasons.
    Bottom problems, loosening of exhaust nut, navigation problems and most important time.
    Getting at the event in time had become impossible... A new approach was needed to prevent such problems in future.

    Critical success factors of our last long rides are:

  • The availability of a Tom-TOM Rider

  • Ditto a big power bank (battery) for smart phone, camera and navigation

  • The ability of speaking and understanding French.

  • Knowledge and skills to repair your mobylette by yourself.

  • An excellent saddle or a standard buddy seat with an extension made of NASA memory foam.

  • A strong mobylette provided with: a variator, strong brakes and all in perfect condition.

  • A special set of lightweight tools and spares.

  • Procedures for standby, whenever the problems cannot be solved by yourself.

  • Enough time for your trip, because you have to count on setbacks.


    In many manuals you can find information about the cause of engine troubles.
    Nevertheless in reality it is often a hell of job to find the malfunctioning part(s). It should be possible to build an interactive knowledge system, that will be able to locate possible failure(s).
    Building a database system, that will contain entities like: cause, part failure, system failure, part and solution, will not be enough for an intelligent expert system. The occurrences of failures can be irregular and different failures can occur at the same time. Theoretically a system may malfunction, though all components are fine when checked in an equivalent system. Lately we solved a lot of strange problems; finding the cause was hard, whereas the solution was mostly quite simple. Nevertheless it is a nice challenge for next winter.
    When a distribution will be available is hard to forecast. So when you have problems read your manuals, visit forums and contact us when nobody can solve your problem.