Crank for Vespa V50

Hi there


Was wondering if someone could point me in the right direction. I have a Vespa v50. I have upgraded the cylinder/pison to a DR75cc kit, a polini banana exhaust, a 16.16 polini carb and manifold kit with reed valve and and 82 jet. 

Its a Swedish imported Vespa and a friend told me here that unlike an italian, or english and german one, the swedes fitted a smaller clutch basically limiting them to a speed of around 30kph, even when kiited out with loads of higher spec parts. 

I was wondering if anyone could suggest what clutch I could fit to my bike that would optimise this set up as there seems to be quite a few to choose from. I dont want to be spending too much but obviously dont want one that will fall apart. 




What you are refering to is the Primary gear (the gear that connects the gear box to the crankshaft, which, is linked together by the clutch, when you disengauge theh clutch (pull the lever in), the gearbox and clutch are no longer connected, enabling you to change gear)


 This Primary gear is available in several different ratios (which is what enables Smallframe models to use essentially many of the same components.

 Basically, a standard 50 (that is limited to 30kmh) will have a primary gear ratio of something like 4.00:1 (which means that the crankshaft turns 4 times, to the gearbox layshaft (sometimes called Christmas tree) turning only once, which as you can understand results in a very high gearbox speed in relation to crankshaft speed, meaning that you have a low road speed in relation to a high engine speed (Termed as low gearing)

 Piaggio simply changed this gear set to suit different small frame models (some aftermarket manufacturers even filled in the missing ratios to suit certain applications as well)

 As a result you can change the primary gear ratio to suit the engine configuration you have, it just means that you have to split the engine completely to change it (keeps you off the streets I guess!)


 Logic would dictate, that going by your cet up, a 3.00 ratio will be suitable


 When you split the engine, pay attention to the conditoin of the selector fork, I like to use the DRT racing selectors, as while they are expensive, they are 100% reliable. (just make sure you select the correct selector for your shaft, as there are 4 different variations of selector, based on what output shaft you have. Good Luck!


HI there


Thanks for the info, a great help. Ill deffo order that tomorrow. Just want to get my bike up and running now. 

So I dont have to do anything with the crank then, i can just leave the stock crank on there?

Ill look into the selector as well, I split the cases a while back and the selector looked ok but was a little worn, I think its been on there since the late 60s. Probably worth changing that too. After all, everything else has been changed pretty much