As fine as Swiss chocolate: series production of the legendary "Ultimo-Giro" Cylinder for Vespa GS150.
The GS 150 is the top model among the wideframe Vespas. No other publicly available model was faster, more expensive and more sought-after. This exclusive tuning cylinder, which was originally designed by Wideframe guru Ralph Bollag from Switzerland, is available to all those lucky enough to own one of these Vespas.
The key data is already impressive:
- Cast aluminum with ceramic coating
- High-quality Piston
- Performance increase with original engine characteristics and noise
- Wide range of tuning options
Finally, a Cylinder with modern technology is also available for this Vespa Model. The aluminum material dissipates combustion heat considerably better than the old grey cast iron and the extremely hard, ceramic-coated bore resists piston wear for much longer. The piston clearance of the Cylinder could be selected much tighter, which noticeably improves performance and makes the engine run more smoothly.
The Piston is a conservative design with a long Shirt and a high silicon content in the alloy. Engine power is noticeably greater than original in every rev range, but without overwriting the original characteristics of your classic car. The timing has been deliberately kept low and the noise is also little changed because the historical intake concept of "slotted timing" has been retained.
However, the SIP Cylinder allows higher revs much more freely than its Piaggio counterpart and therefore cannot deny its pedigree from a winning racing team. The generous, one-piece exhaust is shaped to optimize flow. The channel cross-sections can be considerably enlarged by adapting the sealing surface. The piston skirt can easily be shortened to increase the intake time. If you want to get even more out of it, mounting holes for a diaphragm intake manifold are already included.
Conclusion: Noble spare part that Reinforces the character of your classic car without distorting it. Reliability and suitability for everyday use are considerably improved. Fits absolutely plug & play, but also offers a wide range of tuning options.
Technical details
- Bore 57.0
- Stroke 57 to 62 mm (with corresponding foot gasket/spacer)
- Conrod 105 to 115 mm (with corresponding foot gasket/spacer)
- Squeeze gap 1.5 mm
- Ignition timing 17° from TDC stat. (24° @ 3,000 rpm var.)
- Spark Plug W3CC / W27ES-U / IW27
- Mixture ratio 1:50 (w. Needle Bearing on Gudgeon Pin)
- Cylinder Head with modern combustion chamber shape and crush surface
- Performance diagram see download area
These SIP products fit perfectly - SIP TIPP:
Notes:
A detailed Mounting Instruction is included with the cylinder kit and can also be found in the downloads.
Crankshaft:
The original Crankshaft with bronze bearing on the Gudgeon Pin is sufficient; however, SIP recommends a high-quality crankshaft with Needle Bearing that can cope with unleaded petrol and a lean Oil - fuel mixture of 1:50. Our SIP Premium Crankshaft 45142200, for example, offers excellent value for money.
- Foot seal spacers 5.0 mm 84124050 allow the use of a long 110 mm Conrod (VM, VL, VB - Crankshaft type). Smoother running and Flange for PX Clutch (no Cone).
- Foot gasket spacer 10.0 mm 84124055 enables the use of the SIP Race Crankshaft 45184500 with extra-long 115 Conrod. order 1.5 mm head gasket 84124015 to compensate for the extra stroke of 60 compared to 57 mm.
Carburettor:
The original Dell'Orto UB23 Carburettor can still be used, but the main and Idle Jet should be enlarged. Recommendation Main Jet min. 105 (Art. No. 40101050) and Idle Jet 55 (40245500). Many GS150 Engines exhibit the phenomenon of stuttering at high engine speeds. In many cases, this is caused by a lack of fuel supply. Fast-Flow Fuel Tap 15878000, new Fuel Hose and drilling out the Float Needle Valve to 3.0 mm are usually the solution. Note: The Float Needle Valve is still available from SIP as a new part Art. No. 40292800.
A related alternative to the GS downdraft carburetor is the inclined-flow carburetor, which SIP stocks under Art. No. 20101700; Intake Manifolds for CP and other drum carburetors are also available: 17981140.
Air Filter:
The original Airbox and Air Filter of the GS can still be used. This is the quietest version. However, the filter foam and mesh should be removed from the Air Filter Box so as not to completely block the air intake. The SIP jetting recommendation refers to an original setup with Air Filter Box and intact Connecting Rubber 17981100 to the chassis. If the Connecting Rubber 17981100 has cracks and holes, the pressure conditions in the Intake Tract will change and the carburetor tuning will lean.
Exhaust system:
The original exhaust of the GS150 Engine can NOT be reused because the SIP Cylinder does not have a large screw thread for connection. However, the systems of the normal wideframes VM, VL, VB etc. will fit. We particularly recommend our SIP Road 2.0 and 3.0 exhaust systems with the large body of the PX and e.g. double tailpipe, Art. No. 24157000, 24157230. Exhaust systems with GS body from various manufacturers such as Sito, CC Corse and e.g. the GPS Road Art. No. 24154000 will of course also fit.
Gear ratio:
If only the Cylinder is replaced and no other performance-enhancing measures such as long-stroke and large Carburettor are taken, it is sufficient to retain the original gear ratio. The Vespa will still be faster as a result of the conversion because the Racing Cylinder reaches a higher final speed than the original. Longer primary gear ratios for the GS are now even available, e.g. in a bolted version from Best Racing Vespa "Benelli" Art. No. 88109800. Z65 primaries are good in combination with a freshened SIP Cylinder. Z64 and Z62 are recommended for Quattrini conversions and similar, depending on the remaining engine configuration.
Package Contents:
- SIP GS150 Cylinder, Ø 57.0 mm
- SIP GS150 piston, Ø 57.0 mm
- SIP Cylinder Head, Ø 57.0 mm
- SIP GS150 Exhaust Manifold Stub
- Cylinder head gasket
