Modern Vespa

So I installed an analog speedo. A repop. Anywho I went out this morning and the speedo needle is not moving. Did a search for how to check where it's gone wrong. I disconnected the top at the speedo and spun the wheel. Nothing. So I re did the bottom hookup. Still no cable spinny. So I saw that trimming the bottom of the outer a touch should help. Did that and the cable spins. Installed the bottom section and spun the wheel. Cable spins at the top. Awesome. Put the speedo on and re did the wheel spin. Excellent the needle moves on the speedo. Put the speedo on and went to go for a ride to double check and nothing. No needle movement. Remove the speedo cable from the speedo and it spins fine.

Speedo is brand new. Shouldn't be that being the issue so I grabbed my other one off the Blue Allstate. Same thing. Cable spins until I put the speedo on.

I'm at my wits end. Wtf is going on here. It worked for a second and now nothing…

Help please!

Is the square on the end of the cable the correct size for the receiver on the speedo?

Yes. Both connections are 2.7mm.

Maybe your speedo drive gear teeth could be worn enough to slip when hooked up but with no load from the speedo unit attached the cable spins when the wheel turns? Did you try grabbing the cable end while turning the wheel to see if it slips?

So frustrating that a simple device like a speedometer can't be reproduced so it actually functions. I'm on my third and it stopped recording mileage

My Rally speedo is whining and screaming like a banshee, I'm sending it off to Speedo King in LA. You could try him, seems to answer emails pretty quickly.

I could but both speedos are BRAND SPANKING NEW!

Just double checked at least with the second speedo and the cable fits in the speedo hole and spins fine out of the scoot. I'll have time tomorrow to check the one in the bike again.

Drive gears are brand new. I'll check and make sure it's not slipping again though just to be safe.

I gave up on speedo.... it's been in a box for the past 21 years, collecting value & still doing 20mph

Is it possible that the cable is just a tad short?
If you still have the old speedo try and see if maybe the engagement point (chuck, mandrel, whatever it's called) is the same distance recessed inside the speedo.

I've given up on my Stella speedo for the moment. Replaced the gear and cable and it worked for awhile. Even with a new gear, it would snag when the wheel rotated in reverse. Read somewhere that the PX gear commonly available is slightly different than the Stella gear. Now the Speedo works for about 15 minutes of riding before the needle bounces all over the place. Like the gas gauge, I don't really look at it anymore.

Years ago, I had a brand new PGO. Basically, the same kind of deal as LML, but from Taiwan. That speedo didn't last too long either. I think it's a lost cause.

Length seems good but I'm no expert there. And neither of my Allstates came with speedos so I'm going into this blind.

I did take the scoot to my allergy shot on Wednesday before having time to investigate and on the way home I stopped to adjust my mix screw and noticed the speedo cable had removed itself from the bottom attachment. Once I get a minute I'll look into it again. Bit busy currently having to build a mini chicken run inside my current set up for the new birbs to transition out of my shop and in the world finally. Gotta transition them into the old flock or else the old ladies will murder them all…

We have speedomotration!
Trimmed the outer down a little bit more and spun the wheel by hand and the speedo moved again. Tightened up the bottom of the cable and went for a ride real quick. Nothing. wtf. Sat for a minute and remember reading that you don't wanna tighten it too much. So I loosened it a touch and spun by hand again. Needle moves, now to go get gas. Get a block away and nothing. I did hit a City of Philadelphia special repaved street, which is like a mine field. So I get to the gas station and shove the cable back in. All good! Put 2 whole official miles on it.

How do I get that cable to stay in though?

What happens when the suspension compresses?
Does it pull it out?

Just saw this now as I'm laying in bed, will check in the morning.

It does not. I rocked her back and forth hard and then spun the wheel by hand and checked the speedo, needle moved fine.

Well, I'm outta guesses, sorry
I've had one stop spinning going over bumps, as something pulled out
(Not completely sure if that was a scooter or drunken escapade though)
Get out the pressure washer and spray that front wheel... get it spinning real quick & see what happens.

Got this sorted. Seems I tightened the attachments too much. Backing off allowed the cable to spin and the speedo works now.

Yay, well done

Still goes wild sometimes. But over all it works. I'll be cruising around 40mph and the speedo needle is all over the place for a little bit before it settles back to the proper speed. Nature of the beast I assume.

That's exactly what mine does. Pretty sure the gear is chewed again. Wish they had made it better. I don't mind if it's inaccurate. Good to have a rough idea of speed.