Modern Vespa

Now what is it trying to tell me??

To reiterate, as part of my rebuild, I installed a new cruciform, spindle and selector box and found that the transmission was slipping into and out of 4th gear causing the scooter to lurch. I (reluctantly) replaced the new spindle and cruciform with the originals and I rebuilt the original selector box and reinstalled it. Now the transmission no longer lurches in 4th gear... but it does in second! (and occasionally in third).

My first thought was that I had a worn cruciform but even with the brand new cruciform, the transmission was lurching. The pic below shows wear on the new cruciform with less than 100 miles.

Also, the transmission clicks in Neutral.

I'm at a loss as to what to try next. Any thoughts?

Man! I feel your frustration. I haven't know gear boxes to be so fussy, but maybe I've been lucky so far.

You didnt mention the washer on the spindle. Still have that?

Are your gears in the orientation they used to be? Odd that it magically didnt have clicking, but now it does with the old parts.

Yes I have the washer and Yes the gears are in the proper order which is what makes this so damned frustrating. It feels like something isn't lined up properly but I don't know what

Might I need a thicker shim for the gear stack?

I'm wondering if the gears themselves could be worn although to my (inexperienced) eye they all looked good

Can you post up pics of the four areas
of the individual loose gears where the cross engages? And both sides of the loose gears (so eight pics total).

Did you measure the gear stack gap with two feeler gauges?

And i'd also replace that brand new cross while you're in there.

The cruciform isn't seating where it should.

Are you sure you're putting it in facing the right direction?

If yes, I think you might need a thicker washer on the selector rod.

Im trying to avoid splitting the cases again but I expect it is inevitable. I'll take pics then

Yes I measured the gap with two gauges. I changed to a 1.25 shim but I'll order a 1.5 as well

I do have another new cross I can use

Yes the cruciform is seated properly.

Which washer are you referring to... the one next to the cruciform or the one on the gear stack?

Piaggio specs between 0.15-0.40mm gap. I usually shoot for right about .15mm. It usually means buying a handful of different shim thicknesses...which kinda sucks because it starts to add up $$.

Somewhere there is a SIP video about checking gear and cruciform alignment before final assembly. It's in one of their engine building videos.

Thanks, I will see if I can find it.

Found it. Starts at about 4:30.

?si=Yje0xybhLJAHwc58

Thanks Orwell84 It's a good piece but tells me that I am going to have to pull the engine in order to view the cruciform alignment. I can do it but I'd rather keep the engine in the scooter while I work on it.

On the other hand, Andre says that if the cruciform is not properly aligned, he would add extra spacers when mounting the selector box. I tried adding two extra gaskets and it didn't make any difference. I think I'll go with more gaskets and see if that changes anything.

Does that make sense? If not, I'll go ahead and pull the engine... damn!

You need to understand what it is you're trying to accomplish.

When the scoot is in neutral, the cruciform sits in a narrow channel formed between 1st and 2nd gear.

Assuming your gears are good and the cruciform is installed facing the correct direction, the reason it's "clicking" in neutral is because that narrow channel is either too far toward the rear tire or too far toward the flywheel.

You need to figure out which direction it is.

Putting extra gaskets on the selector box isn't going to help if the neutral channel is too far toward the rear wheel. Extra - or thicker - selector box gaskets only move the cruciform toward the fly wheel.

If the gears are out of alignment in the other direction, either:

- The gears are incorrectly installed on the input shaft

- The hub bearing isn't fully seated in the case

- The shaft isn't fully inserted in the hub bearing

- The selector box isn't correct

- The rod that connects to the cruciform isn't the correct thickness or is missing a washer.

Thank you Socalguy. Your explanation really clarifies things for me. I see that I am going to have to do some research to find the problem

I understand that extra gaskets will help if I need to move the box toward the flywheel but what do I do if I need to move the box in the other direction?

Are there actual metal shims available for the selector box or do you just use the standard cork gaskets?

Getting there.

To solve the problem of the transmission slipping in and out of 4th gear (and sometimes 2nd or 3rd) I added three extra gaskets under the selector box and things are better now. Yesterday I took a run with my Vespa Buddy Steve and rode for about 30 miles without a lurch so what that tells me that the problem was a matter spacing.

Thanks to SoCalGuy and Orwell84 for their helping me pinpoint the problem.

Now that I know what to do, I am going to replace the original selector box with the new one I was using earlier because the original is really hard to operate. By the end of yesterday's run, my left hand was really tired. The new box works much more smoothly and is far easier to operate so I'm going to put that back in place and then determine the number of gaskets I will need to add.

As I say, I'm getting there.

GOTCHA YA BASTARD !

After learning that I could control my transmission with shims under the selector box, I took off my old box and put on my new one with two shims, along with new gear shift cables, and So Far, So Good. The transmission did not shift out of gear and back in again during a two mile test run so I'm counting that as a Win. I'll do a longer run later this week.

I did not put in a new cruciform simply because I didn't want to split the case... again. That can wait for another time when I'm really, really bored.

While the shifting with the new selector box is much better than with the original, it's still damned difficult... especially when shifting into First. I'm guessing that that is probably just the nature of this transmission although I would be open to any suggestions for a smoother operation.

Well, maybe not quite.

I thought I had figured out how to stop the transmission from jumping out of gear with multiple gaskets on the selector box but when I replaced the original 1977 selector box with a new one, I can't keep the transmission in 4th gear with any number of gaskets.

I can hold the shift lever in place for 4th gear and it jumps out of gear less often but I'm wondering if the fact that I have to move the lever so far that the indicator dot nearly lines up with the "lights" mark is telling me something. Any thoughts?

I want to keep the new selector box as shifting is substantially smoother but I don't know what I should do next.

i'd be interested to see both sides of the individual loose gears (where the cross makes contact). Did you happen to take pics of them before you reassembled the cases?

What brand shifter box did you install?

Wrong or crappy (F.A. Italia) selector box…

I had the same issue a while back, see this post:
Transmission Adventures VBB Style
Found I had ordered the wrong selector rod, evidently there is an early model and later model style.
Not sure what scoot you have but mine is a 65 VBB2
The exact same 3rd and 4th and neutral clicking symptoms you have.

No, I wasn't smart enough to take pics of the gears. "They looked good to me!"... but then I have minimal experience with gears. I'll take a lot more pics if I can't avoid splitting the case... again.

It's been suggested that maybe 4th gear is in backwards. I know that I replaced them in the order in which I found them but it's possible that the PO got in there and reversed something.

I did install a new cruciform and spindle.

I don't know the brand of the selector box. This is what I bought.

That's a good piece chippieboy...if I have to split the cases, I'll definitely refer back to it. In the meantime, I'll have to check to make sure that the selector rod hasn't come unscrewed.

I finally gave up on my transmission problems and took Red Rover to Hotrod Al today to ask for his help. His recommendation is that I split the cases again so we can get a better look at what is happening and then go from there. Damn! I was hoping to avoid that

This time I ll take pics

Good plan. Especially with pro help. You have wrestled with that box for a long time. No shame in getting some help.

It's too long!!

I bit the bullet and split the case this morning and tried to install the new cruciform that I picked up a few weeks ago as a spare. When I tried to spin it into the drive shaft, I found that it wouldn't pivot into position... the non-rotating arm is too long. It measures 55.81 mm as compared to the old cruciform which measures 55.67mm.

I'm ordering a new cruciform from Scooter Mercato (I didn't buy the problem cruciform from them) but I'm wondering if it's possible to file down the problem cruciform .14 mm so that it will fit. I'm guessing that doing so would cause problems but I thought I would ask.

I only buy Piaggio cruciforms. I don't know who produces them for Piaggio but they're different, quality wise, to every other aftermarket brand out there...

Got a sip brand cruciform last week. Came it it's own little sip box. First time, hopefully not shite.

I've ordered a new cruciform for Red Rover and while I'm waiting for it I checked the gap under the shoulder washer and it measures .013 in/33 mm. Is that ok? I know I have a list of specifications somewhere but I can't find it.

I currently have a 2.2 washer installed but I'm wondering if I should go to a 2.4 washer.

Any recommendations?

Pics of gears. Just in case? Though it is sounding like an out of spec cruciform is the culprit.

Could someone help me with this please. Is .013 still too lose? What should it be?

I took the gears to Hot Rod Al today and he checked them out and found that there was no noteworthy wear. We measured the various dimensions of the new and the old selector boxes and found some variances so I am going to re-install the gears and the original selector box and see if I can adjust the shifting pattern using shims.

I had everything working fairly well with the original selector box a couple of weeks ago but the shifting took a lot of effort so I re-installed the new selector box as it shifts more smoothly. Unfortunately the new selector box is causing the transmission to shift out of gear and we couldn't fix it with shims.

I've rebuild the original selector box so hopefully it will operate more smoothly and stay in gear.

Also, for what it's worth, I am going back to using the original spindle with a new cruciform. When i started the rebuild I bought a new cruciform but found that it wouldn't thread more than one turn onto the original spindle. I bought a new spindle and the new cruciform screwed on with no problem.

Yesterday, with nothing to lose, I forced an old cruciform onto the original spindle and apparently "adjusted" the threads on the original spindle enough so that I could turn the cruciform down into position. I repeated the process with several other old cruciforms I had lying around and could eventually get them all into position. For that reason, I am going to go back to the original spindle with a new cruciform even though I will have to force it into position. Who knows, it might help.

When you remove the "forced" cruciforms, does the thread still look ok? Instead of using cruciforms to correct the thread on the spindle, how about using a good old 8.8 nut (or higher)? Provided the thread hasn't been messed up and that the bond between spindle and cruciform is solid, i.e. when the cruciform hits the end of the spindle thread it doesn't feel like it wants to keep going; I'd go ahead and (strong) loctite them together.

Regarding the gearbox play, I'm not sure which units you're referring to. It should be close to 0.15mm (max 0.4mm according to the manual), but I've gotten away with 0.09mm.

Scooter Center says this, but I don't know if that's a mistake, because they also indicate the manual figures on their website.
👇

Piaggio says 0.15mm to 0.40mm is acceptable. I shim them to 0.15mm…

I've only installed 2 new cruciforms, but both were on the tight side when installing on the spindle, enough for me to take it off and check the threads on both parts.

I can't do that. I'm afraid… The spindle and cruciform have reverse threads so a standard nut will not work.

I have found that the threads on the original spindle are harder than those on the cruciform so the new cruciform adjusts to the old spindle. I will tighten everything up with loctite

Stupid me, you're right! Forgot all about that...

Getting in Trouble While Waiting for Parts!

I can't work on my transmission until my parts order arrives next week so I thought I would see if I could improve the sound of my stock horn... I mean, how tough could it be?

I should have known better because I've gotten myself in trouble many times asking that same question. Bottom line is that I now need a replacement horn and I'm wondering if anyone is holding one they wouldn't mind getting rid of. I had a backup horn for years but finally gave it away a couple of months ago thinking "I'll never need this"... but of course, now I do.

If anyone has has a P200 horn that they want to sell of, please PM me.

When I split the cases on Red Rover, I discovered that there is no plastic oil slinger. I bought a new one but it doesn't fit. I'm wondering if this scooter ever had a slinger and if I realliy need one now.

Red Rover is a 1977 P200 and I wonder if the design has changed over the years.