How are stud bolts installed on a Vespa?

As part of our Platonika project, which we are putting on the wheels together with Maryzabel, we are also preparing many important assembly steps in videos as tutorials.
Our first tutorial shows the important differences between the different types of studs and the correct assembly.
Common questions such as

  • "Which side is screwed into the motor housing?" or
  • “Will the stud bolt be glued in?”

will be in this Vespa tutorial answered.

In the Vespa range, the threads of the original stud bolts have a "thick" and a "thin" side.
The thread is shorter on the thin side and longer on the thick side.

The side with the thicker thread is screwed into the motor housing and clamps there automatically, provided the motor housing is intact. The stud bolt is thus secured against self-loosening. The free length that remains above the engine housing is determined by the cylinder and cylinder head.

Different variations

In addition to the different lengths of the thread, there are other features to distinguish them.
Here are the most common:

- Rounded end or paragraph

If one of the ends is rounded or clearly set off by a stud bolt and the other end is flat, the rounded side points towards the cylinder head and the side with the flat end is screwed into the engine housing. Stud bolts with a shoulder also make it easier to assemble the washers and nuts in the cylinder head later.

Stud set -M7 x 140mm

-Marking on the shaft 

On one side of the stud bolt, a marking in the form of a ring is attached below the thread. The marked side points towards the cylinder head and the side without a mark is screwed into the engine housing.

Studs -M8 x 160mm

-Blow or point marking on the face 

If an end face of the stud bolt is marked, which can be a point, a star or a kind of cross, this is the free side of the stud bolt and the opposite end is screwed into the housing.

Stud -M7 x 59mm- 22-17-20mm

- solid screw lock

Stud bolts with screw locking applied by the manufacturer are easy to recognize by the material. The side with the screw locking device, which is clearly visible in the color blue, green or red, is screwed into the housing. The free side is blank, without any application of security.

Studs -M8 x 165mm

-Special cases

are, for example, stud bolts that have a clearly marked side but whose installation side to the motor housing does not have a thicker thread. These stud bolts are to be mounted with screw locking.

Stud set -M7 x 158mm

Installation of the stud bolts on Vespa engines

In order to mount the stud bolts securely, we offer this simple but ingenious one Stud mounting set on. As a result, the stud bolt is securely fixed when it is screwed in and cannot simply twist, as is often the case with two locked nuts.

Stud assembly tool set -BGM PRO- M6 / M7 / M8


SC Tutorial Engine Casing Studs bolts (activate subtitles)

Vespa Platonic

Platónika is the name of the scooter. A Vespa PX that we use with new parts from the Scooter Center Create a completely new warehouse. Of course we use our best BGM parts. Benefit from our know-how, get lots of tips and take a look behind the scenes.
Follow the project here in Scooter Centerblog

Watch all the videos in our YouTube channel

This is how you mount stud bolts correctly

Brake drums, cylinders, motor housings - stud bolts are often used everywhere. The locking nut method is often used for assembly. We have even seen pliers in use ... it doesn't have to be:

Gentle and easy assembly

Replacing these studs is very easy with a tool that is easy to grip.

BGM72KT 006

Our Tool for stud bolts is specially designed for the requirements of switch scooters.

All sizes can easily cope with a short piece of thread and can also be used in confined spaces.
Precisely because the assembly tool manages with a very short piece of thread, it should be ensured that the minimum screw-in depth is achieved.

BGM72KT (4)


Special tool for Vespa, Lambretta and Co.

Special cases are, for example, the stud bolts on the engine housing or on the cylinder outlet. It is tight here and the stud bolts are very short. A conventional tool with a roller clamp would inevitably damage the thread or cannot be used sensibly due to the limited space available.

BGM72KT 001

Our BGM tool does not load the thread of the stud bolt. The actual clamping takes place via the integrated ball that engages the end face of the bolt.

BGM72KT 015


Due to their small size, the little helpers are also good for every tour in one Luggage box to stow away.

BGM72M6 (1)

The tools for mounting the stud bolts are available in set or individually in M6, M7 and M8.


BGM72KT (1)




Stud mounting tool
Clever tool from BGM for damage-free installation and removal of studs.

Screw the BGM Pro tool onto the stud bolt and counter with the integrated hexagon socket screw. It is braced with the thread of the stud bolt. Now turn the outer wrench flat. The stud bolt is fixed and is loosened or screwed in. Make sure that the counter-locking is sufficiently strong so that the tool does not come loose.

Ideal for short bolts (such as with Lambretta gearbox covers). The required minimum length of tangible stud thread is: M6 / / M7 = 6,5mm M8 = 9mm

Available individually or as a set.
Also available for the rare thread size M7!

Additional tools required: Open-end / ring spanner: SW19 Allen key: 6mm