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Full Circle Crankshaft BSG

for BSG engine case for Vespa
reed valve, stroke 54,4mm, conrod 115,0mm,
cone 25/20mm, M12x1.25


Alongside Falc, Quattrini and Co. BSG offer some of the hottest tuning parts available to date. The three letters that make up the company name originate from the surname initials of high-end tuner Fabio Begani, racing legend Stefano Scauri and ET-3 wizard Alessandro Graiani. We could stop explaining right here because these guys don't do things by halves. Quite on the contrary BSG and the BSG supported pilots belong to the premier league of Italian scooter racing. Be it in the VPI (Vespa Pista Italia), the CIA (Campionata Italiano Accelerazione) or the new POLINI Cup. With a stunning performance of 48PS, the BSG smallframes was the most powerful scooter on the dyno at the Customshow in Landsberg 2013. It's clear that special components are required to rein such power.



This CNC machined crankcase represents an ideal basis for the extreme performance possible when these BSG parts are properly combined. A full-circle crankshaft, especially developed for this motor, is its heart.

These BSG full-circle crankshafts are extremely solidly constructed. They are manufactured in a small engineering workshop which primarily produces parts for use in Moto GP race bikes, guaranteeing a high end quality. The bearing collars on both sides of the crankshaft have a diameter of 25mm and 20mm for the oil seal collar. The shaft stump, upon which the primary drive is located, has a diameter of 17mm making it 3mm thicker than other similar crankshafts. This peculiarity makes the use of the BSG gear cogs essential. A primary drive holding nut and woodruff key are also included with this kit. Both crank-webs measure a mighty 90.6mm in diameter and are each 20.2mm thick. These full-circle webs are also provided with heavy metal balancing weights to enable them to be very finely balanced, guaranteeing a smoothly running motor throughout the whole rev-range. The con-rod, originally a Moto GP component from APRILIA, is especially stable during use due to its reinforced design. The most widely used version has a length of 115mm with 110 and 105mm lengths also being available from stock. The longer con-rods facilitate a higher primary compression, denser fuel charge and improved performance in the complete rev-range. This crankshaft is available with either a 54.4 or 56mm stroke, with the 56mm version being the more popular size used. When combined with a 60mm bore cylinder the cubic capacity reaches a whopping 158cc! This BSG crankshaft is only compatible with the crankcase also produced by BSG and cannot be used in standard specification motors. This is the most extreme crankshaft that we have ever encountered for the Vespa Smallframe motor! Who dares wins!

Conclusion: Little wonder that, in combination with a BSG crankcase and a suitable performance cylinder kit, over 40PS can be achieved!


Full-circle HPC crankshaft / 54.4-56mm stroke / 105,110 & 115mm con-rod lengths / 20, 25mm / M 12

Full-circle crankshaft with 90.2mm diameter crank-webs, fine balanced, 105/110 & 115mm Moto GP con-rod lengths, oil-seal collar : 20mm, bearing collar diameters : 25mm, large crankshaft stub with a M 12 thread, a small-end bearing / woodruff keys & M 12 nut are included.


SIP-TIP : Do not forget to order suitable oil-seals and bearings. The BSG produced crankcase and primary drive cogs are essential!

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Product forums
icon scootermodels This product fits the following models
divider Producer/Model divider cc divider Type divider Engine divider Yr. of Const. divider Extra
VESPA 50 / N 50 V5A1T 2T AC `63-`71
VESPA 50 L 50 V5A1T 2T AC `66-70
VESPA 50 R 50 V5A1T 2T AC `69-`83
VESPA 50 S 50 V5SA1T 2T AC `63-`84
VESPA 50 Special 50 V5A2T 2T AC '69-'72
VESPA 50 Special 50 V5B1T 2T AC '72-'75
VESPA 50 Special 50 V5B3T 2T AC '75-'83
VESPA 50 Special Elestart 50 V5B4T 2T AC '75-'76
VESPA 50 Special Elestart 50 V5B2T 2T AC `72-`75
VESPA 50 Special Elestart 50 V5A3T 2T AC '69-'72
VESPA 50 SR / Sprinter 50 V5SS2T 2T AC `71-`79
VESPA 50 SS / Super Sprint 50 V5SS1T 2T AC `65-`71
VESPA 90 90 V9A1T 2T AC `63-`84
VESPA 90 Racer 90 V9SS2T 2T AC `71-`74
VESPA 90 SS Super Sprint 90 V9SS1T 2T AC `65-`71
VESPA 100 (UK) / 100 Sport (US) 100 V9B1T 2T AC `78-`90
VESPA 125 125 VMA1T 2T AC `65-`67
VESPA 125 Primavera 125 VMA2T 2T AC `67-`83
VESPA 125 Primavera ET3 125 VMB1T 2T AC `76-`90
VESPA PK 50 50 V5X1T 2T AC `82-`84
VESPA PK 50 S / Elestart 50 V5X2T 2T AC `82-`84
VESPA PK 50 S Lusso / Elestart 50 V5X2T 2T AC `85-`88
VESPA PK 50 SS / Elestart 50 V5S1T 2T AC `83-`86
VESPA PK 50 XL / Elestart 50 V5X3T 2T AC `85-`90
VESPA PK 50 XL FL 50 V5N1T 2T AC `90-
VESPA PK 50 XL HP 50 V5N2T 2T AC `91-`91
VESPA PK 50 XL N NUOVA 50 V5X5T 2T AC `89-`90
VESPA PK 50 XL Rush / Elestart 50 V5X4T 2T AC `88-`90
VESPA PK 50 XL2 / Elestart 50 V5X3T 2T AC `90-
VESPA PK 50 XLS 50 V5S2 2T AC `86-
VESPA PK 80 S / Elestart 80 V8X5T 2T AC `82-`86
VESPA PK 80 S Lusso / Elestart 80 V8X5T 2T AC `85-`88
VESPA PK100 S / Elestart 100 V9X1T 2T AC `82-`84
VESPA PK100 XL 100 V9X2T 2T AC `86-`90
VESPA PK125 125 VMX1T 2T AC `82-`85
VESPA PK125 ETS / Elestart 125 VMS1T 2T AC `84-`85
VESPA PK125 N NUOVO (FL) 125 VMX7T 2T AC `90-`91
VESPA PK125 S / Elestart 125 VMX5T 2T AC `82-`84
VESPA PK125 XL / Elestart 125 VMX6T 2T AC `86-`90
VESPA PK125 XL2 125 VMX6T 2T AC `90-

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