SIP PERFORMANCE Uncle Tom Crankshaft, 54mm, connecting rod 105mm, Vespa 50 45029100
for Vespa 90-125/PV/ET3/PK80-125/S
- Reed valve
- Stroke: 54.0mm
- Connecting rod: 105.0mm
- Shoulder diameter: 88.0mm
- Race - connecting rod
- Connecting rod bearing: 15x19x20 mm
- Piston pin Ø 15mm
- Cone: 20/20mm
- Ø Alternator side oil seal seat: 20 mm
- Ø Bearing seat on alternator side: 20 mm
- With fine balance
High-end crankshafts for Vespa smallframe reed valve engines
Thomas Dolischka, from Austria, has earned a reputation among vintage scooter enthusiasts that extends far beyond the borders of the Alpine republic. In the idyllic tranquility of Vorarlberg's Rhine Valley, he has conceived and built many spectacular scooter projects, and has also thoughtfully designed and manufactured special components for racing. He is particularly renowned for his crankshafts, which he marketed in small production runs, known as "Uncle Tom Crankshafts." Minimal engine vibrations. Bell-shaped, particularly suitable for reed valve setups. High-quality materials and manufacturing techniques.
- Minimal engine vibrations
- Bell-shaped, particularly suitable for lamellar installations
- High quality materials and production techniques
These crankshafts were considered well-built and reliable, but unfortunately Thomas discontinued production, and these popular crankshafts were no longer available. Since Thomas only stopped production due to lack of time and later became convinced of the quality of our SIP Performance crankshafts, he fortunately gave us the opportunity to continue production. This opportunity to resume supplying these sought-after items was gratefully accepted!
Installing these crankshafts
Most versions of Uncle Tom crankshafts feature an unusually long connecting rod. To fit them properly, the engine cases will require modification and machining. The general rule is that 1 mm of clearance around the crankshaft once assembled is sufficient for effective use. Before machining the crankcases, always check that there is sufficient material for the modification. On largeframe engines, it's usually sufficient to lightly machine the flywheel side of the crankcase and remove the valve disc seal material only in the larger half. Vespa smallframe crankcases also require rounding the area between the cylinder base and the crankcase to make room for the connecting rod.
Conclusion: High-end crankshafts that offer the perfect opportunity to undertake long-lasting tuning measures in maximum performance areas!
Specification:
- Bell-shaped for reed valves
- Forged and polished connecting rod
- Generous bearing cooling slots
Specific References
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Questions
| Salvatore Barbara on 18/12/2025 |
Question: Buongiorno, gentilmente potrei sapere la misura effettiva delle spalle di questo albero? In rete trovo pareri discordanti. Grazie anticipatamente per la risposta. 18/12/2025 |
Answer: Da misura diametro spalle 88mm 19/12/2025 |
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