Crankshaft BGM PRO Evolution 2 Long Stroke 55 mm / 110 mm – Piaggio Maxi 125–180cc 2T

Description

High-performance crankshaft BGM PRO Evolution 2 Long Stroke is intended for tuning Piaggio Maxi 125–180cc 2T engines. The version features an increased 55 mm stroke, 110 mm connecting rod and full crank webs with a diameter of 90 mm.

Compared with the standard version with a 52 mm stroke and 105 mm connecting rod, the 55 mm version allows an increase in displacement and more possibilities when adjusting the cylinder port timings. The longer 110 mm connecting rod also contributes to smoother operation and reduced side load on the piston.

Technical specifications

• Manufacturer: BGM PRO
• Series: Evolution 2
• Type: Long Stroke
• Crankshaft stroke: 55 mm
• Connecting rod length: 110 mm
• Crank web diameter: Ø90 mm
• Version: full-circle webs
• Precisely balanced construction
• Strong connecting rod
• For Piaggio Maxi 125–180cc 2T engines
• Intended for higher-performance engine tuning

Suitable for

• Aprilia SR 125
• Gilera Runner 125 FX
• Gilera Runner 180 FXR
• Italjet Dragster 125
• Italjet Dragster 180
• Piaggio SKR 125
• Piaggio SKR 150
• Piaggio TPH / Typhoon 125
• Piaggio Skipper 125
• Piaggio Skipper 150
• Piaggio Hexagon 125 EX
• Piaggio Hexagon 150 EX
• Other models with the corresponding Piaggio Maxi 125–180cc 2T engine

Special features of the 55 mm version

The standard crankshaft uses a 52 mm stroke, while the BGM PRO Long Stroke version uses 55 mm, which means a total of 3 mm additional stroke.

At the same time, a 110 mm connecting rod is used, which is 5 mm longer than the standard 105 mm connecting rod. Because of this, the cylinder position must be adjusted accordingly during installation and the additional stroke must be compensated for.

The longer stroke allows:

• increased engine displacement
• more possibilities for adjusting cylinder port timings
• use in higher-performance tuning configurations
• the longer connecting rod reduces piston side load
• smoother engine operation

Important for installation

To compensate for the 5 mm longer connecting rod, a suitable 5 mm spacer is required, which is not included.

This 5 mm spacer compensates only for the difference in connecting rod length. The additional 3 mm stroke must be compensated for separately by 1.5 mm, either:

• with a 1.5 mm gasket under the cylinder, or
• with a 1.5 mm gasket or suitable machining of the cylinder head.

When using a 1.5 mm spacer under the cylinder, the cylinder port timings also change. Such a setup is more suitable for a sport configuration with higher operating rpm, but additional adjustment of the exhaust port may also be required for optimal operation.

For engines intended for everyday use, the manufacturer generally recommends compensating for the additional stroke on the cylinder head side.

Note

Due to raising the cylinder, the position of the exhaust connection also changes. With certain configurations, it is therefore necessary to adjust the position or mounting of the exhaust so that it can be fitted correctly to the cylinder and engine without tension.

This is a tuning crankshaft for which correct installation requires checking and appropriately adjusting the cylinder height, squish, port timings and exhaust position.