Extensively redesigned crankcase for Vespa Smallframe models, newly developed and manufactured by SIP.
The SIP Smallframe crankcase looks nearly 100% like the original but has been significantly reinforced in all key areas. This makes it your top choice for original replacement parts and serious tuning.
- Suitable as an original replacement
- Plenty of material at the overflow ports and intake for tuning
- Reinforced and durable design
The overflow ports and intake are original size but can be significantly enlarged without welding. The material thickness has been substantially increased to provide sufficient material for milling. The intake has a massive sealing surface and can be enlarged beyond the casing parting line—that is, on both sides of the casing.
The lower housing bolt connection is offset outward to allow for mounting crankshafts with larger web diameters or strokes. 100% protection against crankshaft breakage, verified by tests in an officially accredited laboratory! To this end, endurance tests lasting 14 days at near full load—with a POLINI 133 / 24 Carburettor / PM Racing Exhaust—as well as temperature, corrosion, and road tests were successfully completed. The results have been incorporated into the design as improvements.
As a further enhancement, high-quality Italian Rubber Engine Mounting Bushs are installed. Before shipment, every single casing is thoroughly measured and inspected. The casing arrives securely packaged in a double-layered cardboard box.
The design is based on the PK casing with a 3-hole Intake Manifold and exhaust mounting beneath the crossbar axis. With our SERIE PRO Intake Manifolds 21500060, 21500070, and 21500080, as well as our exhaust adapter, it is easy to use the casing as a replacement for Vespa 50-125/PV/ET3 models.
The Different Variants
We offer two housing versions with different alternator bearing seats: for ETS crankshafts with the Vespa PX bearing, or for original Vespa 50-125/PV/ET3/PK50-125 bearings with a 47 mm outer diameter.
Since 2019, we have also been able to offer the original 2-hole Intake Manifold variant. These casings combine the advantages of the SIP PK crankcase with the features of the older Smallframe engines: 2-hole intake manifold mounting, a circular intake passage, and a smaller intake port on the rotary valve sealing surface, as well as 3 additional screw domes for very old Stator Plates with only 2 coils.
This allows an old engine to be rebuilt 100% true to the original using a new SIP casing. The enclosed parts certificate confirms the authenticity of a Vespa 50–125-cc engine rebuilt with a SIP casing. This should also please dealers, given their warranty concerns.
The SIP EVO crankcases have even more material to mill on the overflow port on the alternator side. However, this requires the Stator Plate to be modified. The intake also has more material to mill. The cooling channel at the cylinder base sealing surface has been removed. The EVO version is also available in a very attractive Black Edition.
Conclusion: The days of small-frame engines failing due to engine damage are over—and at the best value for the money!
Features
- Fits Vespa 50-125/PV/ET3, with Adaptor Intake Manifold or in a 2-hole version, as well as PK models
- Original appearance and port sizes, very large sealing surfaces, additional material for milling and tapping
- The cylinder base sealing surface covers the entire area on both half-cases—for maximum sealing surface area with machined transfer ports/cylinders
- Increased wall thickness and reinforcement ribs inside the engine, on the crankcase, and on the Suspension Arm
- In the EVO version, with even more material at the intake and alternator overflow port, as well as an adapted fan duct
- 3 crankcase versions available for alternator bearings: Ø 47 mm, 20-series Shaft, in 2- or 3-hole configurations; and Ø 38 mm, 25-series ETS Shaft
- The Suspension Arm is reinforced on the inside and designed for use with 3.00- and 3.50-10 tyres. 3.50-10 tyres fit without modifications
- The pre-installed Rubber Engine Mounting Bushs result in a total width of the Engine Swing Arm Pivot of approximately 195 mm. This provides additional stability and can be beneficial for warped frames. If necessary, the dimension can be adjusted in just a few simple steps
- The primary bearing seat has been optimized and has an outer diameter of 57.5 mm to accommodate all primary gear ratios and repair kits
- Proven design in vibration, endurance, and road tests
- Replaceable bronze bearing sleeve for the Selector Arm
- The package includes studs for the Brake Baseplate and Casing (2 x)
- Kickstarter stop rubbers and Rubber Engine Mounting Bushs on the Suspension Arm and Shock Absorber Seating are already installed
- The EVO version is also available as a Black Edition
- The 2-hole version with TÜV parts certification
These products fit perfectly – SIP TIPS:
- Don’t forget the Gasket Set, Oil Seals, Bearing, Woodruff Keys, and Gearbox Oil. A new casing will also benefit from new reinforced cylinder studs, engine bolts, and nuts.
- Riders with a 2-hole Intake Manifold will also need a conversion Intake Manifold (21500060, 21500070, or 21500080). Those who want to use crankshafts with a 54 mm or 56 mm stroke can opt for casings that have been specially bored for this purpose.
Feedback from the scene
“We tested the crankcase you sent us and we’re satisfied; we used it in the Polini Cup on Sunday with good results.”
–Paolo Pavanati, PARMAKIT, Italy, July 15, 2016
“Already put it to use! Awesome casing with a really long rotary valve intake ;-)”
–GSF User Mike, Germany, April 29, 2016
“In my opinion, SIP has hit the nail on the head. For €460, you get a new casing that’s easy to modify and doesn’t have the problems you had with the old ones.”
–Et3.it Community User ROS04, Italy, August 21, 2015
“I finally got to use my Dremel on it—great material, doesn’t stick, even on the CNC. It’s a GREAT material.”
–Et3.it Community User $ aplus, Italy, May 2, 2016
“Finally, a top-notch crankcase in standard width for building race engines! Where the Quattrini blocks have long since been scraping the road because they’re wider, the SIP crankcase still has plenty of clearance. Thanks, SIP!”
–SIP customer MaNiAc, Germany, June 13, 2016
