Speed thrills! PARMAKIT, together with Italian racing champ STEFANO SCAURI, has stormed the market with their purebred SP-W-Force.
SP stands for Sport Production, and W-Force means a reed valve direct intake in the hottest up to date W-Force version. Move to the head of the class with 2 separate reed valve casings instead of just one to get an optimal flow surface. The reed valves star in the successful Aprilia Rotax cylinders. Double dipping here: they are fed not only through the intake, the generous Boysen port is the other side of this successful hottie.
The exhaust port is bridged, with an exhaust width of 82%. VERTEX delivers the piston and offers either a 58 mm or 60 mm bore coated forged piston with a 1.0 mm piston ring. Timing of both cylinder kits is identical. All cylinders in the SP W-Force series have a larger base diameter. The crankcase must be modified and, at the very least, the cylinder base adapter will have to be milled.
58.00 mm -> base adapter in casing 63.0 mm, tolerance +0.03 - +0.05 mm, 20.0 mm deep.
60.0 mm, 97 mm connecting rod -> base adapter in casing 65.0 mm, tolerance +0.03 - +0.05 mm, 20.0 mm deep.
60.0 mm, 105 mm connecting rod -> base adapter in casing 65.5 mm, tolerance +0.03 - +0.05 mm, 7.5 mm deep measured from original gasket surface.
The squish clearance should be at least 1.3 mm, exact adjustment through spacer included in delivery. Exhaust stud distance 62 mm, exhaust system must be modified, for example with a modified flange plate.
Conclusion: This race cylinder is true to it's name: performance of 28 PS can be achieved and maintained.
Aluminum/ 58/60 mm bore/ 5 transfers/ 135/144 cc's
Aluminum cylinder, 51 mm stroke, 97 mm or 105 mm connecting rod, 5 transfers, direct intake, W-Force reed valve, VERTEX forged piston with 1.0 mm cast piston ring, bi-conical gudgeon pin, 8 mm exhaust studs with 62 mm stud distance and 36 mm exhaust diameter, 8x screwed, centered CNC milled two piece cylinder head with separate combustion chamber (anodised), incl. gasket set.
Motor periphery should match performance increase and jets should be adjusted. Fits all Vespa PV/ET3/XL/XL2 models, except PK automatic. The crankcase must be modified to match the larger cylinder transfers.
SIP-TIP: Main jet adjustment and new spark plugs are a must. Racing shaft with 20/20 or 24/25 end cone. Pay attention to length of connecting rod. Exhaust VSP Race, FRANZ or FALC, electronic ignition such as VESPATRONIC or PARMAKIT, carburetor 34 - 38 mm. Primary 2.54 - 2.34, round out with DRT toothed gears.