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- Vespa Classic
- Crankshaft - BGM Touring 57 mm stroke - Vespa Sprint 150 (VLB1T), GL150 (VLA1T), GT125 (VNL2T), GTR125 (VNL2T), VNB, VBA, VBB, T4, Super
The BGM PRO Touring crankshaft for the Vespa VBB and Sprint is specifically tuned for high-torque street engines. Thanks to the rotary valve intake —which opens earlier and is longer than the stock version —a longer effective intake duration can be achieved without any modifications to the engine case. This improves cylinder filling and delivers strong low-end torque as well as a noticeable power gain across the entire usable RPM range. The intake start at the crankpin is 3°, and the total opening angle is 120°. Highly recommended in combination with the BGM 2-channel cylinders.
The BGM PRO Touring Crankshaft was developed for classic Vespa large-frame engines such as the VBB and Sprint, where a powerful, responsive engine character is a priority. A key advantage over a stock crankshaft is the optimized control of the rotary valve intake.
The crankshaft journal is designed so that the rotary valve opens earlier. This is a significant advantage, especially for early Vespa rotary valve engines with comparatively short stock intake durations.
The earlier intake start is achieved directly through the contour of the crankshaft. This allows the effective intake duration to be extended without having to machine the rotary valve intake in the engine case. This makes the shaft particularly appealing for engines where the original housing should remain as untouched as possible.
In addition to the earlier opening time, the BGM PRO Touring crankshaft offers a longer intake angle than the original crankshaft. This gives the engine more time to draw in fresh air through the rotary valve intake.
The improved filling isn’t just effective at higher RPMs. Combined with the early intake timing, this results in an engine that responds powerfully even at low RPMs and delivers noticeably more torque and power across the typical street RPM range.
The intake valve timing, optimized compared to the stock version, supports early torque build-up and improves intake efficiency across the typical RPM range of a touring engine.
The characteristics of the BGM PRO Touring crankshaft harmonize particularly well with the BGM 2-channel cylinders. This combination better harnesses the potential of the classic 2-channel engine cases without losing the typical everyday practicality and torque-oriented character of these engines.
Especially for VBB and Sprint engines, this crankshaft thus enables a highly effective upgrade: more usable intake time, better filling, and more powerful engine performance—without requiring the engine case to be milled to accommodate the earlier intake start.
Conclusion: The BGM PRO Touring crankshaft is the ideal choice for classic Vespa rotary-slide engines when the goal is to achieve early, strong torque, better filling, and more power across a wide RPM range—without necessarily having to machine the rotary valve inlet of the engine casing.
