Modern Vespa

Howdy. Still sorting thru things on my recent up-from-the-junkyard V100 build.

I thought I finally had the shifting and transmission in order. Everything has been fine as I drive around my quiet local streets, which are flat. It's a 3-speed.

Then, today, I took it on a longer ride over a hill, and, while going uphill, the bike either popped out of 3rd gear or the clutch lost all grip. The effect what that I was happily tooling along, and then—pop!—the engine was just spinning, as tho I were in neutral.

When it happened the second time, I gave up and continued the short trip in 2nd gear. No problems.

When it slipped, I MIGHT have been lugging the engine a bit. I'm new to this and might have been shifting too early.

My thought was that maybe the clutch was slipping—that it isn't adjusted correctly and it gave way. Although there's free play in the lever.

I've had no problems in first or second, and no problems in 3rd when I'm on level ground. This happened in 3rd, only going uphill, and maybe at relatively low RPM. I might have been accelerating as well.

Thoughts? I'm a noob and trying to think this through, but I'm finding that my first guess about Vespas isn't always right . . .

Muchas gracias

Hi there!

My first thought is that the clutch is ok as long as it is ok when using 1st and 2nd gear....

So that makes me think of either worn gear selector and/or too much play in gearbox (out of tolerance between the gears on the rear axle)...


So it sounds like you have a full split of engine coming up.

Easy stuff first: Have you properly adjusted the shifter cables and the clutch lever cable?

Thanks, guys. Here's something else: There seems to be enough "space" between 2nd and 3rd that, when I'm shifting, the tabs on the shift cross will actually spin in there—as tho I'm in neutral—if I don't continue the shift until the shift cross "clicks" into place. I assume that's normal (the tabs need a moment to spin between the two gears, i.e., where they're not connected to either gear)??

Part of the problem here is that I don't really know what's happening when I feel the sudden loss of power to the axle. Has the clutch given up or has the shift cross become disengaged from 3rd gear? And, if the latter, where the heck has the shift cross gone?? Is it spinning between second and third? Is there any scenario where the tabs could move BEYOND third gear??

If anyone can tell me how to clearly determine whether the problem is the clutch or the cross, please let me know. Meanwhile, I'll put a little more slack in the clutch, to make sure it's fully closing.

Merci.

Also (gulp); Is there any way this could be a symptom of my stacking the gear stack wrong? Maybe, somehow, the cross is barely grabbing in 3rd, and slipping out when I put a big demand on the gear??

This noob has a feeling for foreboding . . .

my primavera had popping out of 4th gear up hills. it could be your selector spring is weak. the guys at scooterwest gave me a trick to use instead of the uprated spring - you can install a 3rd ball with a standard spring. that sorted mine. i had a power upgrade to a DR130 with Polini pipe though.

is your engine still stock? you didn't really say.

A very good point! Didn't think of that possibility. No, it's no longer a stock 100. I too have a power upgrade to a 130, with a banana exhaust.

I'll ask ScooterWest what they think . . .

I really appreciate your chiming in. Thanks.

You're probably going to want more holding power for that selector then. It's very common once you up the power.

Ahhhhhhh. Fascinating to reverse-engineer this, in one's mind, especially as a noob. Suddenly losing power to the axle in third, but only uphill, means:

—the clutched isn't fully engaged, so it gives up when you ask a lot?

—there's something up with the selector, or maybe the shims aren't right?

—I've stacked the gears wrong, third is only partially engaging, and pops when there is too much demand?

—the detentes don't hold because I've upped to a 130 p & c, and the selector spring is now too weak?

That last one would have NEVER occurred to me. Thanks very much for pointing it out. I'll check with ScooterWest too but, either way, it looks like I'm splitting the case.

And, as long as I'm in there (again!!) I'm going to upgrade to a 4-speed.

Yeeeeehaaaaaa!!

Wow way to take advantage of the split. Watch out for the early/late differences in transmission components (pk vs. early).

I have had this happen a number if times and it is because I am gripping the shifter too hard and bump it into false neutral. Try relaxing your grip.

Solved, tho not completely sure which change did it. As I was going to have to drop the engine to fiddle with the selector spring and ball bearings anyway, I decided to change from 3-speed to a 4-speed (on a 100 it's very straightforward—the new 4-gear stack fits the axle perfectly, and then it's just a matter of switching the Christmas tree and shift-cross).

With all that, I replaced the spring and ball bearings and now everything works as it should. 4 speeds and no popping out of gear, even on super-steep hills. Cool.

Also, the $15 "small frame selector spring tool" is a godsend.

yes, the tool is required - and a plastic bag over the tool while inserting the balls to keep flying ones from going into the corner of the shop

I'd say the tool is suggested, but not required. The plastic bag is absolutely required, unless you want to play hide-n-seek with a 4mm ball bearing in your workshop.

Oh, and when the clutch is slipping you'll hear the motor speeding up, but the scooter not accelerating with it.

For an extreme example, watch 00:35-00:45 of this video:

OK - tool not required, so long as you don't value your sanity or free time. Even more so if you are trying an uprated spring.

I value my free time, but clearly don't value my sanity.

I think I tried fourteen times before succeeding without the tool. At one point the ball bearing literally shot across the living room, bounced off the flat TV screen, and landed in a pot lid on the stove.

If it had shattered the TV I would have been noticeably unhappy. (Didn't know about the plastic bag. Oops.)

With the tool it was first attempt and less than a minute. And my family says I'm much easier to live with.

I think I tried fourteen times before succeeding without the tool. At one point the ball bearing literally shot across the living room, bounced off the flat TV screen, and landed in a pot lid on the stove.

If it had shattered the TV I would have been noticeably unhappy. (Didn't know about the plastic bag. Oops.)

With the tool it was first attempt and less than a minute. And my family says I'm much easier to live with.