Modern Vespa

I'm hoping some knowledge folk on this forum might be able to help with an issue I'm trying to resolve.

I have a 68 primavera 125 that I have owned for around around a year now an issue developed where, when cruising along, and sometimes when throttling hard, in mainly 3rd and 4th, it would feel like it was skipping out of gear momentarily for a half a second then jump back in.

I took her to two separate shops to try and fix the problem, both having no luck.

I decided to have a go myself! When stripping down the engine I found the woodruff key for the clutch was in two pieces so I though this could have been this issue. I also checked the clearance of the main gears and adjusted the clearance down to .23mm with new spacers as per the manual. I couldn't find any other issues so I began putting things back together.

When I was about re attached the gear cables I was moving through the gears by hand and notices if I move the gear shifted very carefully and slowly by hand I can find what feels like a neutral between 3rd and 4th gear.

Before I go any further, I just wanted to check if this was normal or not?

Thanks,
Ollie

It sounds like you need a new cruciform and maybe your gearbox spacers are out of spec.

It's pretty sad that two shops failed to diagnose such a common/normal issue.

Check your gears and see if the lands (the slots where the cruciform contacts the gears) show signs of wear. If so, you're going to need to replace some gears, too, which is sadly a lot more expensive than a cruciform.

Post up some pictures, both of the parts and your scoot. We love pictures!

Thanks for the advice. I have now stripped the engine back down so I can examine the internals again.

Looking again, It appears the issue (as you suggested) is caused by warn gears and or cruciform. It seems quite clear that there is to much space between 2nd - 3rd and 3rd - 4th so the cruciform can spin between these gears. I haven't been able to measure the thickness of what remains on the gear tabs. I have also uploaded a video showing the issue.

Here a load of photos of everything + photo of the scoot!

To me, the corners of the gear slots and the cruciform do not look bad. The gap between gears is necessary so that two gears can not be engaged at the same time. The gap between first and second is greater for a true neutral position. Maybe your cables are adjusted to tight and you are inadvertently moving the grip while accelerating? I have done thin many times while going up hill, for instance.