Yet another moped speed calculator, specifically for Piaggio/Vespa/Gilera belt driven mopeds, like the Ciao, Bravo, Si etc.
My own testings show pretty accurate results, you typically need to input a little higher tyre size, because the rim size isn’t measured at the furthest point of the outer edge. Cross check with the tyre circumference. The pulley diameters should be measured on the outside of the belt, so wrap one around your pulleys and measure the diameter with a caliper. In some pulleys the belt sits lower than the outer diameter.
You need MS Excel, OpenOffice, LibreOffice, GDocs or similar to open the file.
I wasn’t happy with the printed on transparent foil decals, that i could buy for my Honda PA50. I’ve created my own, a copy from an old original. It’s made in Adobe Illustrator and is in vector format, so a plotter can cut it in foil.
Another spreadsheet i’ve made, to calculate the speed of your moped at a given RPM. You need to know the details of your engine, gearbox, sprockets and rear wheel. You can find most of it in a spare parts catalogue, or simply count the teeth on all sprockets.
I’ve made a spreadsheet that you can use to calculate the ingition timing, to convert mm before top dead center to degrees, and reverse. I think the file is self explanatory, click the link below and try it out.