Modern Vespa

Hi guys,

I fitted a 24/72 primary together with the 102cc Pinasco, 1st and 2nd speed will be much more fun and usable. Original on my 75 smallie is way too short 14/69.

Which 3rd and 4th "shorter" gear options do I have, in combination with the input shaft? My gear cogs are 58, 54, 49 and 43 tooth (input shaft 10, 15, 21, 26). I will have to change 3rd and 4th to i.e. 50, 46 … and then which input shaft do I need to go with them?

I have one input shaft 10, 14, 18, 20 - 4th doesn't even touch the 43 cog. Will a 46 4th cog work or the input shaft has to be something like a 10-14-18(20?)-22 with a 50 3rd and a 46 4th ?

Sorry so many numbers and questions, surely they're simple and clear for people used to tune up smallie engines…
Thanks

I see DRT has a 10-14-17-20 to work with a 50 3rd and 46 4th

Would my 10-14-18-20 work fine too with those two?

Ps: It seems most 10-14-18-20 go with the 50 and 46 for 3rd and 4th. What a bummer me thinking would fit this input shaft and keep the gear cogs

Update (good news):

The 50 and 46 gear cogs (CIF) go well with the input shaft (VMC) 10-14-18-20
As I'm typing I guess engine is beeing closed ... can't wait to try the redesigned gear box with the 102cc

That was a journey!

Update: Alive and kicking, The new gearing ratios worked great with the 102cc

A new a$$ too

Gearing is the most under-appreciated aspect of engine tuning. Good job.

Thanks, indeed a shame if I didn't review gearing with a bigger cylinder. From 1st to 4th, a joy to use, top speed maybe around 80 km/h but that already scares me on this tiny frame. What I notice is changing gears is more difficult now, stiffer, any gear including the ones I didn't change cogs (1st and 2nd) … due to the new cruciform and spring… ? In speed is better but at slow speeds I need to act "firmly". But engages fine and never skips or miss, its just harder. I think it needs some milleage to burn in.

Regards