If you find that oil drips gather on the clutch arm then the O-ring on the shaft is the probable cause.

Vespas are not supposed to weep oil: that is a job for old British motorcycles and badly assembled Lambrettas. With age though, comes incontinence and after a few years you may find that your Vespa starts to leak, particularly if you make it sneeze or giggle.

 The most common culprit for these oil leaks is the clutch cover. The simple solution is to remove the cover and replace the O-rings: both the large one around the outside rim and also the smaller one on the shaft of the clutch arm. What happens when that doesn’t work and it still leaks?

Sticky

The cover is quite easy to remove. Take off the rear wheel, undo the clutch cable nipple and remove the three clutch cover bolts. If the cover is tricky to separate you can lever between the arm and the casing.
The cover is quite easy to remove. Take off the rear wheel, undo the clutch cable nipple and remove the three clutch cover bolts. If the cover is tricky to separate you can lever between the arm and the casing.
The arm is only retained in the hosing by the spring. If you hold the cover in a vice by one of the bolt lugs then you can use a pair of pipe pliers to turn and unhook the spring from the cover before pulling the shaft out.
The arm is only retained in the hosing by the spring. If you hold the cover in a vice by one of the bolt lugs then you can use a pair of pipe pliers to turn and unhook the spring from the cover before pulling the shaft out.
Good quality ‘complete’ gaskets sets contain a new O-ring for the clutch shaft and a large one for the housing. Sometimes fitting new O-rings cures the problem, but not always.
Good quality ‘complete’ gaskets sets contain a new O-ring for the clutch shaft and a large one for the housing. Sometimes fitting new O-rings cures the problem, but not always.
The problem is that dirt gets inside the bore hole where the shaft runs and together with the O-ring it wears a groove in the aluminium making leaks hard to cure without completely replacing the clutch cover.
The problem is that dirt gets inside the bore hole where the shaft runs and together with the O-ring it wears a groove in the aluminium making leaks hard to cure without completely replacing the clutch cover.
The simple solution is to take the clutch arm to an engineer and get a second O-ring groove machined into it further up the shaft. The groove should be identical to the original one in width and depth. The difference is that this second O-ring will run against virgin aluminium. The other alternative is to fit a slightly thicker O-ring in the original position (original is 9mm inside diameter x 1.7mm section) though this may increase stiffness of the clutch action. Both 9 x 1.8mm and 9 x 2.0mm are available.
The simple solution is to take the clutch arm to an engineer and get a second O-ring groove machined into it further up the shaft. The groove should be identical to the original one in width and depth. The difference is that this second O-ring will run against virgin aluminium. The other alternative is to fit a slightly thicker O-ring in the original position (original is 9mm inside diameter x 1.7mm section) though this may increase stiffness of the clutch action. Both 9 x 1.8mm and 9 x 2.0mm are available.
Grease the shaft and reassemble the arm along with the cam that fits in the centre of the cover. A dab of grease is useful to hold the activation pad in place while the cover is refitted. This is such an effective modification that at least one dealer I know does it to every PX engine he rebuilds.
Grease the shaft and reassemble the arm along with the cam that fits in the centre of the cover. A dab of grease is useful to hold the activation pad in place while the cover is refitted. This is such an effective modification that at least one dealer I know does it to every PX engine he rebuilds.
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