Cylinder -POLINI 177 cc 3 Ports cast iron- Vespa PX125-150, GTR125 (VNL2T), TS125 (VNL3T), Sprint150 Veloce (VLB1T 0150001-)

After the conversion everyone is amazed how powerful a Vespa engine can accelerate. The beary torque turns every steep mountain into a plain.
The only disadvantage is that the Polini doesn't turn very much. At about 7000 rpm the engine runs a little bit in front of the wall, a longer transmission ratio by means of another clutch pinion is recommendable in any case. Then the Polini easily exceeds the 100km/h mark and the gears can be pulled much longer.

If you are only driving in the city you can use the 24/24SI carburetor of the 200cc models. The carburetor should be driven with a 160 main air jet and a BE3 mixing tube. If the engine still tends to slim down in the upper rpm range a 140-150 main air jet should be fitted.

If you want to go on a big tour with the Polini you should fit a 28-30 mm carburettor for thermal relief. The 177 harmonizes well with exhaust systems that give off their power quite early, such as the BGM BigBox.

In combination with a bgm long-stroke combustion shaft the power output is again increased considerably over the whole speed range. The result is a hefty 187 cc, which provides power in abundance. If you are still not satisfied with this, you can use a file to increase the already quite small forward exhaust angle. The result is a power output which, depending on the exhaust, can easily exceed 15 kW.
For tuning measures which entail an enlargement of the exhaust window and an increase of the working speed, it is recommended to exchange the original piston rings for Grand Sport models. These are much less prone to breakage and can withstand the increased loads well. For further performance increases above the 25hp mark there is also a complete piston with much thinner rings from Grand Sport.

TIPP: Please always mount piston rings carefully. Piston rings made of cast material are only conditionally elastic and break relatively quickly.
Some pistons have trapezoidally profiled piston rings (so-called keystone rings), these only fit in one installation position. If the ring does not move freely, please loosen it carefully and reinstall it upside down.
are very helpful tools for working on the cylinder and/or piston:

• Piston ring compressor -BUZZETTI- Ø=45-90mm BU5040
• Piston ring pliers BU5045
• Dismantling tool for piston pin -UNIVERSAL- Ø=13, 15, 16, 19, 22mm 7674333