I now want to upgrade the gearbox to a 4-speed gearbox. The cush gear will have a 13-13-17-21 cluster and the loose gears will be 56, 42, 38 and 35. I can fit a clutch gear with either 21t or 22t, and I can change the primary gear between 67t or 68t.
I have put all these values into the Vespa Gearbox Ratios spreadsheet, but to be honest with you, I don't know how to interpret the results. Your help and recommendations would be appreciated.
⚠️ Last edited by danie on UTC; edited 1 time