The setup: 2003 Vespa ET4 with the Leader engine, Malossi variator, 14g weights, Malossi belt, Contra spring and Delta clutch. 800 miles showing. SitoPlus exhaust recently installed. Still with stock gearing. GPS Speedometer phone app displayed on the right mirror. (Minor wind resistance? Yeah, not worth 1MPH.)
The Course: Over the Copano Bay Bridge, roughly a 2-mile span with clearance for most recreational sailboats. Not a super-tall bridge. Right Quartering tailwind going north, headwind coming back.
I didn't pump up the tires, full load of fuel - and mail - Piaggio top box and short windshield. No Danskin suit, either. And Wheelman don't tuck. One more thing about conditions; Temp was 92-ish at the airport. God only knows on the pavement. Humidity was sky-high too. Pilots out there will tell you what happens to power with air density low and humidity high.
Speedometer error approaches 20% at low speeds. (24 indicated = 20 GPS) The error seems to decline at higher speeds, perhaps due to tire stretch or increased speedometer needle spring tension?? Whatever the reason, 60 Indicated = 55 GPS, or about 9%.
Going UP - remember 12Kt quartering wind astern - I was able to manage 67 and stable. Cresting the top, GPS climbed to 72 and would climb no further. Speedometer was approaching 80! but don't be fooled... Coming back with wind ahead from the left, it managed 62 GPS on the climb and 68 on the descent. I was hoping a pickup would pass and be drafted. I neglected to look at the tach when I reached VMax, but the Tuff Tach recorded 9000 peak RPM. Considerably faster than I recall before the SitoPlus, but I'll go back and check. [EDIT: My previous-best top speed was 61.4GPS on my Introduction to ISO post. Tach reading was under 8200. I must credit the SitoPlus pipe, as I've made no other changes...]
More to follow as I install the Polini Primaries. Next big project will be the Malossi 187. Almost ready to sell my other kidney to buy it...