Adapter set J&G2% for PX 200 cylinder mounting on PX 125-150 casing

Description

Adapter plate set for conversion PX80/125/150cc engine to PX200 cylinder 12hp.
Which rider of a Vespa with only 80cc or 125cc has not dreamed of experiencing the torque and sovereignty of a 200cc engine in his vehicle?
Powerfully and casually enjoying a mountain pass road without having to constantly use the lower gears?
More power and still have the full reliability of a 200cc engine?

All this is now possible based on an existing 80-150cc engine.
With the long stroke shaft included in the kit, the engine performance of a stock 200cc engine can be significantly exceeded.
In combination with the BGM200 cylinder (improved replica of the series cylinder) are with a good exhaust (eg BGM BigBox Touring V2 or Polini Box) stable performance values in the range 14-16HP possible with a very good torque of 17-20Nm at the rear wheel. With an original Piaggio cylinder it is usually but also still considerable 13-15HP at the rear wheel.

The adapter set is suitable for the following vehicles:

Vespa Sprint Veloce150 (VLB1T 294260-)

Vespa GTR125 (VNL2T 145901-)

Vespa Super150 (VBC1T 412374-)

Vespa TS125 (VNL3T 18139-)

Vespa PX80 (V8X1T), PX125 (VNX1T, VNX2T, ZAPM093), PX150 (VLX1T, ZAPM74, ZAPM094)

Vespa Cosa125 (VNR1T), Cosa150 (VLR1T)

LML125/150 2-stroke

Star/Stella 125/150 2-stroke

After an idea from Geoff (J&G 2% Vespa Tuning) as well as the technical implementation by W.T. we have subjected the set extensively and long a full stress test on the road and highway. The result is so convincing and reliable that we can now offer it as a set for the experienced screwdriver. It allows the use of a Malossi 210 Sport cylinder of the PX200/Rally/Cosa models on the engine cases of the Vespa Largeframe models from 1977 onwards. From this date onwards, the engine cases were converted to three overcurrent channels or to the crankshaft of the PX models (here, for vehicles before 1980, pay attention to the border chassis number). Generally the set fits on every engine with three overcurrent channels as well as the crankshaft type PX (recognizable by a pole wheel nut with M12 thread).
The adapter set includes:

The adapter set includes:

Crankshaft BGM Touring stroke 60, connecting rod 125mm

1x adapter plate steel 14mm

1x spacer aluminum 1.5mm

4x stud bolt M8x165mm

4x screws M7x25mm

To convert this engine to 200cc you need beside the adapter-set further

Cylinder+ cylinder head PX200

Exhaust PX200

Longer gear reduction

Reinforced clutch


ADAPTER-SET
The conversion is based on a crankshaft with 20mm longer connecting rods (125mm instead of 105mm).
The solid CNC machined steel adapter plate bolts onto the engine case and accepts the studs for the PX200 cylinder. A 1.5mm thick aluminum gasket between the adapter plate and cylinder base seals the bolt holes and establishes the correct headroom.

ORIGINAL CYLINDER (no case spindling necessary)
The adapter set SC80200KT (without crankshaft) or SC80200SET (incl. crankshaft) is designed for use with an original (or close to original) PX200 cylinder. Here, the existing cylinder is only shortened slightly at the base (use adapter plate as a template). This can even be done with a simple hacksaw or flex. The nicer solution is of course the turning on a lathe. It is important to make a chamfer at the end of the cylinder bore so that the piston rings can be easily inserted into the cylinder. But we will also offer directly fitting cylinders. These are based on the BGM200 cylinder, which already has a little more power/torque than the standard cylinder. If you have the possibilities, you can also enlarge the engine housing in the area of the cylinder base (spindle up). Then, in the future, any cylinder that also fits the original PX200 engines can be used (except for cylinders that already require a longer connecting rod (e.g. Quattrini)).

CURB SHAFT
The BGM crankshaft fits the engine case of the PX80-150cc models without modifications.
It has adjusted timing angles and harmonizes perfectly with the intake of the PX80-150cc models.

CARBURETTOR
The standard carburetor (SI20/20D) can be kept as long as it is adapted by the jetting (use basic tuning of the PX200). However, more power and torque is provided by the carburetor of the PX200 models (SI24/24E). This also has directly the appropriate jetting. For the installation of the SI24 carburetor, the carburetor bowl should be adjusted in the passage (this is done quickly with a file or a Dremel/Proxxon tool).

TRANSMISSION
In order to make good use of the significantly higher and early torque, the reduction should be extended:
80cc
The PX80 has its own secondary gearbox which is very short (originally, the third gear of the PX200 is already longer than the fourth gear of the PX80). If the PX80 gearbox is to be retained, it can be used with an extra long reduction primary from e.g. BGM (25/62). This is used in conjunction with a stable COSA2 type clutch, e.g. a BGM Superstrong clutch. Alternatively, with minor modification work, a gearbox of the PX125/150 models can be used in the PX80 engine cases.
To do this, either the auxiliary shaft axle is turned down in diameter on the alternator side or the engine housing is enlarged at the mounting for the auxiliary shaft.

125/150cc
For the 125/150cc engines it is sufficient to change to the components of the 200cc engines on the primary side (primary gear 64Z (BGM) or 65Z, clutch pinion 23Z or 24Z (BGM).

CLUTCH
The 80-150cc models still use small clutches with 6-springs (108mm basket diameter) until 1998. These are permanently not up to the high torque of the 200cc engines. Therefore, this should be changed against a corresponding clutch of the 200cc models. A good possibility to change directly to the most modern clutch type of the COSA2 models. Here there is with the BGM Pro Superstrong a very high quality and stable clutch which is also easy to use.

IGNITION/POLER
These can be taken over from the donor engine without any problems. The ignition setting is according to the cylinder (18°-23° v.o.t.). Of course, other ignitions/pole wheels can be used for further tuning purposes. Our test engine ran with the pole wheel BGM Touring with 2300 grams which harmonizes very nicely with the performance characteristics of the 200cc engines.

CYLINDER HOOD
Due to the 15mm increase in the height of the cylinder, the cooling hood must also be extended accordingly. We simply used two hoods and cut off the lower third of one of them. This we have then connected with conventional sheet metal screws with the complete other hood. Of course, this can also be solved more nicely, but for us, this method has proven itself in everyday use. Alternatively, the hoods can be welded together with a soldering iron. Special plastic welding rods are also available for this purpose, but as a rule you can also use the remnants of the sacrificed hood as filling material.

EXHAUST
Due to the higher cylinder it can happen that the exhaust must be adjusted. Our experience has shown that the Polini box systems must be modified (twist the retaining tabs). The BGM Touring V2 systems (BGM1011TR2) however worked on our setup without any adjustments.

CYLINDER DISASSEMBLY
Due to the raised cylinder it is not possible to disassemble the cylinder head/cylinder while the engine is installed in the chassis. Alternatively, the stud bolts can be countered with our BGM72M7 tool and unscrewed from the adapter plate when the cylinder is mounted. This allows the head as well as the cylinder to be removed with the engine hanging in the frame. Normally this is a procedure that is not recommended as the threads in the soft aluminum of the engine case are not designed for frequent de/assembly. The original Piaggio studs have a thickened thread on the side where they are screwed into the engine case, which causes them to jam in the case.
However, due to the other stud bolts used by us and the adapter plate material made of steel, this is completely uncritical.

CONCLUSION
Anyone who enjoys engine work and is not afraid of small adjustments can build a powerful and durable engine with little effort without having to use a new engine housing.