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The machinings on the engine block are divided into two areas: the inlet and the overflow ducts.

Here are usually still hidden PS. Especially with Vespa and Lambrettamotoren, it is useful to rework the overcurrent channels. Often, old unsuitable over-current channels have to be welded to the housing in order to be able to mill suitable and flow-efficient channels. Basic rule: The undisturbed the gas flow the better.

Overflow channels

worb5 vespa lambretta engine case overflow channels

These adjustments are absolutely necessary for the Vespa PX 200 in conjunction with Polini or Malossi cylinders.
After welding the overflow ducts, the sealing surface of the engine housing (where the cylinder is to be installed later) is planned since aluminum weld metal is present at the location of the overflow ducts.
worb5 vespa lambretta engine case

In addition, it is necessary to rewind the mounting hole of the engine housing for the cylinder foot so that the cylinder fits again into the engine housing. In the last operation, the overflow ducts are milled and polished into the engine block, with the respective cylinder being presented.

worb5 vespa lambretta engine case
If a 130 cc Polini in the reworked version (5 mm aluminum plate and large ducts) or a reworked 136 ccm Malossi cylinder is installed in a Vespa Smallframe should be welded in here also somewhat on the Limaseite (the ignition anchor plate must be spared a little) , at 2 points on the cylin- der side and at the cylinder foot sealing surface on the engine block. The engine block can easily be retrofitted, since it is only in a small place.

worb5 vespa lambretta engine case

The milling and polishing of the overcurrent channels is also useful for a Lambretta. For example, an RB cylinder is enlarged on the channel side must also be applied to the motor block on material.

Often it is nowendig the crankcase inside in diameter to enlarge around the crankshaft and also the connecting rod place to offer. This is usually necessary when large strokes are implemented. We can mill crankcase CNC.

To convert the intake at Vespa PX engines to diaphragm inlet should be welded on the coupling side. Without welding, the intake duct is properly enlarged on the clutch side. The inlet is milled and polished. Likewise, the exhaust port is still reworked here and there.
Also with Smallframe motor housing it is sensible to weld the inlet material on the outside in order to be able to mill the inlet as large as possible.

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