Because the flywheel fan of David´s Vespa was in a really bad condition we think that the cheaper (and aestetic) solution could be modify the stock flywheel to mount an a Polini fan from a Evo ignition set.
After have the Polini fan on our hands I started to sketch both parts to model it on Solidworks and get the new profile, for machine the destroyed fan blades on the CNC lathe.
Stock Vespa PK 75 XL flywheel.
Polini fan from a Evo ignition set (David do not want recognize but I´m sure he will mount the full set soon).
....ready for a turning....
The surfaces in red were machined to remove the damaged blades and fit the new fan and we did four new M8 threaded holes to mount it. Also we remove the internal pivots of the fan.
Around 200 grams less, isn't a great loss but (for the moment) not it´s our target.
Exploded view of the sub-assembly.
To save some money we reuse the old cover, a coat of matt black can do miracles....on this pic we still must cut around 5mm radial and paint again.
The final result (lack a final paint coat on the fan cover) looks much better than before, few money expended and the clockwise oriented blades of the polini fan will give much more fresh air to the cylinder.
As usual I uploaded the 3d models to my profile in Grabcad and 3dVia. Click on the images to open the files on both pages.