Full Circle Crankshaft SIP BFA 306

A very sturdy, vibration-free full-circle webbed crankshaft, produced specifically for the BFA Vespa largeframe crankcases.

Every two-stroke motor possesses the advantage of consisting of only three moving parts; The crankshaft, con rod and piston. This simplicity also saves an awful lot of weight, when compared to other combustion motor types. This is also the fundamental reason that these components are so essential in the tuning of Vespas. This has been consequently realised by BFA in the construction of this crankshaft and have dimensioned it accordingly.

• Heavy duty for smooth running engine by mass between crankshaft bearings
• Long, high-quality connecting rod with good lubrication of the bearings
• Very stable due to wide design and high quality materials

In order to enable it to successfully withstand higher-than-standard performance values any crankshaft requires sufficient material surrounding the more relevant positions to provide more stability during use. A certain quantity of rotating mass is also necessary to provide a smoother running motor, ideally concentrated surrounding the areas where the forces causing the vibrations are most apparent. It is also practical when the crankshaft itself is provided with a certain amount of mass to especially, but not exclusively, be combined with more powerful motors.

Very strong webs

The crankshaft in this BFA kit is noticeably more sturdily dimensioned, with a total web width of 54.4mm and a 102mm web diameter. This range of crankshafts weigh from 3.5 Kg (original crankshafts weigh about half) according to type. This provides sufficient rotational mass to noticeably improve both the smooth running and stability of the motor. Despite its massive dimensioning this advantage in weight could only be achieved by the use of heavy-metal crankshaft web plug-inserts. An involved but extremely effective method of providing the crankshaft with sufficient mass.

The forged con rod

The BFA crankshafts are all equipped with forged and polished con rods, with a length of between 120mm and 135mm. Generously dimensioned lubrication slots are provided, at either end, for both the big and small-end bearings.

The new clutch stub

One of the more unusual and perhaps interesting features concerns the version with a redesigned clutch-side crankshaft stub. The first version retains a standard-style clutch attachment assembly and the other comes equipped with a fixed cog-style attachment option. This makes the connection between the crankshaft and the clutch extremely durable and also more stable. This solution requires however the inclusion of a suitably compatible clutch type, equipped with an identical cog-style attachment set up. This system no longer requires the potentially nerve-racking mounting with a woodruff key and slot! Clutches that spin or heat-seize to the crankshaft become a part of history!

Conclusion : The complementary high-end crankshaft and also technical kingpin of the excellent game-changing crankcases from BFA!

The technical specifications at a glance :

• 54.4mm total web width,102mm web diameter, weight: 3,5kg
• 60mm stroke (187-225ccm) or 64mm (306ccm)
• Tungsten crankshaft web insert plugs
• Forged and polished con rod
• Optional cog-style clutch mounting available
• Including piston pin bearing, woodruff key clutch side and clutch nut

The Best Setup - Our SIP-TIP :

• SIP BFA crankcase absolutely necessary
• Do not forget to order crankshaft bearing art.-no.  90056100/90056200 and shaft seals art. no. 91033700/91033800, as well as PX woodruff key flywheel side and nut
• The crankshaft can be gently installed with this tool art. no.  10052700

Please note: During mounting pay attention to the positioning of the bearing. The BFA crankcases are already equipped with their own bearings with the fixed bearing being located within the flywheel side of the engine casings.