Modern Vespa

So your speedo stopped working. You need to determine if the problem is
1- a worn gear in the gearbox:)
2- a broken cable:-
3- a broken speedo:(

The first is easiest to both diagnose and fix, (and cheapest), so you should always start here. Unscrew the gear plate and wire retainer thing from the left front wheel gearbox, and pull the cable out. Try spinning the cable quickly in your hand while having a friend look at the speedo. It should register a low speed when the cable is spinning. This tells you the cable and the speedo are AOK, and you don't have to mess with the upper part of the bike.

( if you really want to be sure about this, and you have an new inner speedo cable gadding about, put it in the front wheel. If the wheel spins forward and the cable does not spin, it tells you the problem is in the gearbox.

You need a new speedo drive gear. Order the part below from Scooter West:
267819 Speedo Drive Gear For All Modern Vespas 1 $8.95
It's the yellowed plastic piece on the far right in the photo below.
image1.jpegimage4.jpeg

Or part number 15 in the diagram above.

When the part comes, again unscrew the gear plate(10), and pull out the speedo cable and plug. Now comes the tricky part....removing the brass fitting(14). Mine was caked with old machine grease, stuck there for 14 years, and really hard to get a grip on. I first sprayed it with wd40 to loosen the old grease. Then used a combo of levering a screw driver through the hole and opening up a pointy nosed plier inside the hole and pulling to eventually worry it free. (Oh happy day). At this point you can see the speedo gear. Spinning the front wheel one way pushes it out enough to be grabbed with a plier. (My gear was also caked with old grease, and worn flat on one side. Sort of glad to see this as it verified where the problem was.). Bad idea to put a new gear in there with hard bits of old grease clogging up the works. Cleaned out the hole with wd40 on a q-tip, and then put the new gear in coated with fresh machine grease, spun the wheel a bit, and took it out. It picked up a load of old black crusty stuff which needed to to be cleaned off. I did this two or three more times until the gear was coming out clean...just coated with fresh machine grease. Then put it in for good.

Popped the brass fitting back in, plugged in the old speedo cable (cleaned of gunk with wd40, and then coated with fresh machine grease) , screwed everything back in, and hit the road. Speedo and odometer both worked great!!

I had purchased a cable and the gear, and never used the cable. If/when that breaks, you'll get installment 2 of the speedo not working saga. Hopefully never need 3!

very helpful post, thanks!
I'm having this exact issue at the moment but it's a broken cable rather than a gear.

The photos I posted never came through... I'm a newbie to the posting on this forum. Good luck with the speedo cable. I liked the idea of just purchasing the inner cable, and threading it through from the top. This will only work if the outer cable is intact, but it prevents you from having to thread a new cable from the top to the wheel, which seemed like it could be a bit tricky. Sometimes the easy fix works just fine.

Just posting a few more things so I'm not a "lurker".

Still listing me as a lurker!

That last one did the trick.

After opening the picture in the browse dialog box, you must click add attachment to upload it.
It helps to edit the photo and resize it to 800 pixels or the photo will be too large.

Interesting that Piaggio/Vespa does not have a maintenance proceedure for checking/adding grease to that area.
(From Vespa tech at the dealer and Service manual)

My gear (Mentioned above) lost all it's teeth in the hard grease.
Yes I live in the desert, and it's hot and I have 30k plus miles on my bike.
I had to pick out all the crumbs of grease with a paper clip, blow out as much as I could and then repacked it with high temp roller bearing grease.
There should be a Wiki on this

I'll submit one after the holidays

Nice write up Geri. Where do you live in NY? I grew up near (actually right on the border) of MA. Small town called Canaan. It's in Columbia county. Don't miss the winters.