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Transfer ports mill engine Vespa PX

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The Vespa engine - the heart of Platonica - has received the desired control angles of the crankshaft in the last article

Cylinder transfer ports in the engine adapt for performance optimization

Before the complete assembly of the motor can be done, all work that generates chips must be done. Only then can the housing be cleaned.

In the next step, this includes the ports of the cylinder in the engine.
The BGM177 is designed in such a way that the cylinder functions perfectly even on the original ports.
However, in our project we took the opportunity to directly adapt the case. A better filling of the cylinder always means a higher possible torque.

In order to transfer the contour of the overcurrent channels to the motor housing, the easiest way is to place the matching cylinder base gasket on the housing and thus transfer the contour to the housing.

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1 Junta Carcasa1 Junta Carcasa

The sealing surface is best marked with a foil pen. Then the contour of the overflow channels is marked with the aid of the cylinder base gasket.

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A milling cutter is then used to adapt the contour in the motor housing. It is not necessary to mill the channel exactly as deep as in the original motor housing.

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The BGM 177 cylinders is designed from the basic construction so that the piston offers a sufficient cross section.
The generated surface of the adapted channel may be milled rough. Further polishing is not necessary. As long as there are no more rough corners and edges, a slightly roughened surface is perfect.

After the channels have been milled and the housing has been cleaned again, the assembly process continues

Scooter Center Tutorial Vespa PX - Modifying the transfers (activate subtitles)

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TUTORIAL - Crushing edge Vespa PX

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How do I measure the pinch point on the cylinder head?

In our second tutorial we describe how to measure and adjust the pinch point of a bgm177 cylinder. Of course, the sequence is applicable for all other cylinders, but the dimensions can vary greatly depending on the manufacturer or the desired application of the cylinder and may differ from our dimensions in the video.

zylinder_bgm_pro_177_187_ccm_kolben_made_by_meteor_vespa_px125_px150_cosa125_cosa150_gtr125_ts125_sprint_veloce_vlb1t_0150001_bgm1770nzylinder_bgm_pro_177_187_ccm_kolben_made_by_meteor_vespa_px125_px150_cosa125_cosa150_gtr125_ts125_sprint_veloce_vlb1t_0150001_bgm1770n

For the heart of Platónika we mounted the bgm177 cylinder dry first.
This means that the piston is initially mounted without piston rings and only with the upper bearing of the crankshaft. So if the cylinder has to be mounted several times to set the correct squeeze size, the threading of the piston rings is bypassed until the final assembly.

The bgm177 cylinder is supplied with several gaskets for the cylinder base with different thicknesses of 0.2, 0.4 and 0.6 mm.

BGM1770G (1) (1)BGM1770G (1) (1)

The cylinder is mounted without a seal for the cylinder base. To map the squeeze size we use soft solder with a diameter of 2 mm.

The length of the piece of solder should correspond to the diameter of the hole. A little excess length does not harm to position the soldering tin with adhesive tape on the piston, parallel to the piston pin.

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The cylinder head is mounted and fixed together with the gasket. By turning the crankshaft the piston is turned once over the TDC = top dead center. There, the solder is squeezed between the piston crown and the pinch-off surface of the cylinder head to the squeeze size, thus forming the current squeeze size.
After the cylinder head is disassembled again, the crushed solder at the ends can be easily measured with the caliper gauge. In our example this results in a dimension of 0.62mm.
The manual of ours bgm177 cylinder gives us as recommendation a squeeze size of 1mm.

bgm_177 instructionsbgm_177 instructions

How do I change the squeeze size?

In order to get to 1mm with the existing squeezing dimension of 0.62mm, a cylinder base gasket of 0.4mm must be added; to get to the desired dimension of 1mm purely by calculation.

 

Scooter Center Tutorial Vespa PX - Checking the piston squish (Activate subtitles)

 

https://blog.scooter-center.com/tutorial-stehbolzen-vespa-px/

 

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Tutorial stud bolt Vespa PX

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How are stud bolts mounted on a Vespa?

In the context of our project Platonika which we are putting on the wheels together with Maryzabel, we prepare many important steps of the assembly also in videos as tutorial.
Our first tutorial shows the important differences between the different types of studs and the correct mounting.
Frequently asked questions such as

  • “Which side is screwed into the engine housing? "Or
  • "Will the stud bolt be glued in?"

are answered in this Vespa tutorial.

In the Vespa area 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.

Short part of the studShort part of the stud
Long part of the studLong part of the stud

The side with the thicker thread is therefore screwed into the motor housing and, provided the motor housing is intact, it clamps there automatically. 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.

Engine case directionEngine case direction

Different variants

Apart from the different lengths of the threads, there are other features to distinguish them.
Here are the most common ones:

- Rounded end or paragraph

If one of the ends is rounded or distinctly offset 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 allow easier mounting of the washers and nuts in the cylinder head later on.

Stud bolt set - M7 x 140mm

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stehbolzen_m7_x_140mm_verwendet_f_r_zylinder_vespa_px80_px125_px150_sprint_gt125_vnl2t_gtr125_vnl2t_ts125_vnl3t_super_vna_vnb_vba_vbstehbolzen_m7_x_140mm_verwendet_f_r_zylinder_vespa_px80_px125_px150_sprint_gt125_vnl2t_gtr125_vnl2t_ts125_vnl3t_super_vna_vnb_vba_vb

-Marking on the shaft

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

Stud bolt - M8 x 160mm

stehbolzen_m8_x_160mm_piaggio_verwendet_f_r_zylinder_vespa_px200_rally180_vsd1t_rally200_vse1t_ss180_vsc1t_gs160_gs4_vsb1t_lambrettastehbolzen_m8_x_160mm_piaggio_verwendet_f_r_zylinder_vespa_px200_rally180_vsd1t_rally200_vse1t_ss180_vsc1t_gs160_gs4_vsb1t_lambretta

-Impact or point marking on the front face

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

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

stehbolzen_m7_x_59mm_22_17_20mm_verwendet_f_r_motorgeh_use_vespa_v50_v90_pv125_et3_pk_s_pk_xl_7675543stehbolzen_m7_x_59mm_22_17_20mm_verwendet_f_r_motorgeh_use_vespa_v50_v90_pv125_et3_pk_s_pk_xl_7675543

- tight screw lock

Stud bolts with manufacturer-applied screw locking are easily identified by the material. The side with the screw lock, clearly visible in blue, green or red, is screwed into the housing. The free page is blank, without any order of backup.

Stud bolt - M8 x 165mm

stehbolzen_m8_x_165mm_piaggio_verwendet_f_r_zylinder_piaggio_quasar_250_300_ccm_7670297stehbolzen_m8_x_165mm_piaggio_verwendet_f_r_zylinder_piaggio_quasar_250_300_ccm_7670297

-Special cases

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

Stud bolt set - M7 x 158mm

stehbolzen_set_m7_x_158mm_polini_verwendet_f_r_zylinder_vespa_v90_pv125_et3_pk80_pk125_mit_kurbelwelle_hub_54mm_p3170111stehbolzen_set_m7_x_158mm_polini_verwendet_f_r_zylinder_vespa_v90_pv125_et3_pk80_pk125_mit_kurbelwelle_hub_54mm_p3170111
screw locking_loctite_270_high-strength_10ml_3600008screw locking_loctite_270_high-strength_10ml_3600008

Installation of the stud bolts for Vespa

To mount the stud bolts safely, we offer this simple but ingenious stud bolt mounting set. This ensures that the stud bolt is securely fixed when screwed in and cannot simply twist through, as is often the case with two countered nuts.

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

Stud_montagewerkzeug_set_bgm_pro_m6m7m8_bgm72ktStud_montagewerkzeug_set_bgm_pro_m6m7m8_bgm72kt

 

SC Tutorial Engine Casing Studs bolts (activate subtitles)

Vespa Platonic

Platónika is the name of the scooter. A Vespa PX, which we completely rebuild with new parts from the Scooter Center floor. Of course we use our best BGM parts. Benefit from our know-how, receive many tips and take a look behind the scenes.
Follow the project here on the Scooter Center blog

Watch all the videos on our YouTube channel

 

https://blog.scooter-center.com/das-herzstueck-vespa-platonika-bgm-177/

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