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Lambretta LD Clutch Explained

The Lambretta LD Clutch Explained

Wet / Oiled Clutch

Lambretta’s run in an wet (oiled) clutch system.  A wet clutch is one that is soaked in oil, as opposed to having no oil in the parts.

Clutch Removal

For information on the clutch removal, see here: Lambretta LD Clutch Removal

Lambretta Teleflex Adjustment – Applies to MK1 D LD C LC

Clutch Plates

Consisting of x2 driven steel discs (02060120) interleaved with three driving (Friction 11061046) discs that are lined with a bonded (5mm) rubber cork-mixture.  Pressure is maintained by six springs (40060105).

125cc & 150cc (& side car) Plates & Springs

On original / untouched Lambrettas, the 150cc clutch unit has (x2) thicker plates and stronger springs than the 125cc model and if a sidecar is used, still stronger springs were available and installed.  Up-rated springs may be found online (Rimini Lambrertta Italy).  The (x3) Friction (lined with cork) disks and springs available online are interchangeable and old parts manuals only show the part numbers above. I do not know a way of checking if the springs are faulty.  However, clutch slipping can be an indication of this problem.

In the drive plate assembly, only some of the plates are always spinning, even though this is connected to the engine all the time. The friction plates are what actually apply the leverage to get the vehicle moving. When these squeeze together, it engages the clutch, and all the discs start moving together. This includes the notched drive discs, which come in contact with the clutch basket.

Drive Plate Assembly

The drive plate actually looks like a stack of pancakes with one friction plate, one driving plate, one friction plate, etc., stacked one on top of another. It is is held together by springs and screws called drive screws, which apply the pressure to the plates, and this needs oil to operate properly.

The clutch springs press the clutch plates together.  If springs are too short or not strong enough, they will not able to separate the plates.

Clutch Slipping Possible Causes

  • Clutch cable to long in relation to the outer cable. Adjust the cable length and then readjust the control pin
  • Clutch driving discs (friction 11061046) are worn and require replacing.
  • Pressure springs (40060105) are weak / broken. Up-rated spring can be found online in some places (Rimini Lambrertta Italy).
  • When the clutch will not come completely free as the control is operated, it means that the cable has stretched and needs readjustment or renewal, especially if the wires have been frayed.
  • It i possible that the clutch linkage or clutch cable simply requires lubrication or adjustment.

Clutch Adjustment (Internal x2 nuts under acorn / dome 19mm nut)

The pressure of the springs, is provided by adjusting two lock nuts (8mm) on the thrust rod within the large brass acorn nut at the forward end of the clutch casing.  Adjusting out the nuts will put some more tension on the cable and give the arm more travel

Note: If the clutch is adjusted too tightly, excessive wear may develop.

Clutch Cable

  • The clutch cable should be lubricated.
  • If the clutch is shifting too tight, the clutch cable may be worn; rusted up or unable to move inside the sleeve. Try removing from the outer sleeve and review.  It may either need replacing, or you may get away with lubricating it.
  • The clutch cable should sit tight in the arm. If it does not, pull the cable tight with a 3rd hand tool and move the nipple up on the inner so that it sits tight in the arm.

Oil Replacement

  • Failure to replace the oil on a regular basis will (Summer and Winter), or leaving your Lambretta standing for extended periods of time may result in the clutch plates sticking together and you may also experience grating when the bottom gear is engaged from cold.
  • Oil that loses its lubricating properties over extended period of time can make gear shifting harder.

Further review works

  • You may need to strip the clutch down & prize all the driven and driving disc plates apart, then clean them (paraffin or petrol / gasoline) and put it all back together.
  • If dismantling the clutch area, during removal, mark matching parts position to be sure to return them to their proper places (Including the discs)
  • Oil on the plates can act as an adhesive after the Lambretta has been stood idle for some time. In theory, this effect should disappear almost at once, but may also require cable adjustment.
  • Similar comment – If the clutch is not disengaging, there may not be enough movement to part the disks sufficiently. Adjusting the length of the cable may help in this area.

Lambretta Serviceman’s Book

From the Lambretta Serviceman’s Book (Page 40) – The clutch is adjusted by the knurled screw at the hand lever, but the cable must not be at all tight and there should be at least three quarters free movement at the tip of the lever.  When no further adjustment remains at the lever end, remove the 19mm domed nut from the centre of the clutch cover on the offside at the front the engine compartment and slacken the two 8mm hexagon nuts locked together on the end of the clutch withdrawal pull rod beneath, using suitable thin spanners.  Set the nuts in a position which will allow the adjustment of the handlebar end to be restored and re-tighten

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