Modern Vespa

I have a false neutral between 3rd and 4th gear.
I have cracked open the engine, and I've noticed that between 2nd and 3rd I have a larger gap.(see photo) I'm not sure if this is normal, or not or if that's going to make any difference.
When I put the cruciform between the gears, while I have them on the workbench, the cruciform will turn between the gears.
I'm using the 2.4 mm spacer and I have a .6 mm gap under the circlip. Any suggestions? Discuss..

Spec for a large frame is 0.15mm to 0.40mm float clearance fully assembled. You have way too much play at 0.60mm! Make sure your gear stack is assembled correctly.

Hec

The gear stack is assembled so that there is a gap between each gear. If I reverse any of the gears, there wouldn't be any gap. I've looked around and the thickest shim is the one I have which is 2.4 mm. Not sure what I can do to make the gap any smaller unless I can get a really thin one to add to it

Gaps look fine to me. Bigger gap between 3rd & 2nd is also normal…

Here is a video done by Scooter West. It helped me. For axle assembly go to Time Stamp 37:54 to 48:12.

Hec

Thanks for all the suggestions but all I need is some way to reduce the gap size. Am I looking at buying a whole new set of gears or is there some other kind of solution?

If your gears are used, there stands a 50% chance that you should replace one of them. There stands a 75% chance that you should replace two of them. You can buy special shims that have different thicknesses. Sometimes you have to buy a handful of them and pick the one that works the best for your gear stack. And of course you already have a brand new quality cruciform that's ready to be installed...

Do you know what the gear thickness should be? I can check it with my caliper.

The thickness of the gears slowly wear down over time. So does the shim and the axle shaft. You will have to install all the gears, shim, and circlip back together. Then get a couple feeler gauges and measure the spacing (you mentioned yours was .6mm). Then do some reverse math and see what what thickness shim it would take to narrow up that gap. Then go buy a few different sized shims that you think will work the best for your application. If you have to buy new gears at the same time, your measurements will most likely change a small smidge. There's no formula to get the exact shim you need on the first try. You just have to have a handful of them and start playing with the different thicknesses.

EDIT: or maybe i misunderstood your question now that i read it again?...

The only time a gear wears out is if there's a broken toofus or if the area where the cruciform makes contact (in other words slams) into the inner portion of the gear. It's VERY common to have a gear that looks perfect everywhere, except for where the cruciform does its crucifying. Then it's time to throw the gear in the bin. Please post of pics so that all of us can see what you're seeing!

The gears look pretty good to me.
Take a look at the pictures

Use 2 - 1.4MM spacers?

Spots like that too. Seems like 2nd gets that particular kind of where. The second gear on my Stella had similar wear, though maybe not as much. I ran it though as it wasn't causing problems.

That's a perfect solution but I can't find that size anywhere.

What about this?

https://www.sip-scootershop.com/en/product/spacer-set-bearing-crankshaft-clutch-side-o-50x62-mm-th-0-1-0-2-0-3mm_90012010?q=Spacer%20bearing%20crankshaft%20clutch-side

Any combination of spacers that gets you under that .4 mm number is OK.

I don't know if anyone's asked this question or not but how does the cruciform look? Second gear is questionable but I don't know if it's necessarily a problem. All the other gears look pretty good.

I don't think you can use multiple spacers. My Haynes Manual lists the available oversized spacers to pick from but does not mention using more than one spacer. I think you will need need new gears, spacers, cruciform, axle or all the above.
Maybe others have tried using multiple spacers with success and they can chime in.

This will be interesting.




Hec

The cruciform was fairly new. It did show some wear on it. Maybe only 400 km on it. But I do have a new one to put in, of course.

That cruciform is really beat up for only 400k on it. And i personally would replace that 2nd gear in a heartbeat. I like all my transmissions to be in tip top shape for long term reliability. Having a damaged gear will only accelerate wear on the cruciform.
https://www.sip-scootershop.com/en/category/classic-vespa_2/spares_1751/vespa-pxt5cosa_T5/engine-vespa-pxt5cosa_1777/gear-box-drive-shaft_1740?model=eyJkaW1lbnNpb24iOiJ7XCJuYW1lXCI6XCJLTEFTU0lLIFZFU1BBXCIsXCJ1bmlxdWVudW1iZXJcIjoyfSIsInNjb290ZXJUeXBlIjoie1wibmFtZVwiOlwiVmVzcGEgUFgvVDUvQ29zYVwiLFwic2x1Z1wiOlwiVDVcIixcImRpbWVuc2lvblwiOntcIm5hbWVcIjpcIktMQVNTSUsgVkVTUEFcIixcInVuaXF1ZW51bWJlclwiOjIsXCJwb3NpdGlvblwiOjEwLFwiYXBpQ29uZmlnX3BhdGhcIjpcInNjb290ZXIvY2F0ZWdvcmllc1wifSxcImFwaUNvbmZpZ19wYXRoXCI6XCJzY29vdGVyL3R5cGVzXCJ9IiwicHJvZHVjZXIiOm51bGwsIm1vZGVsIjpudWxsfQ%3D%3D

https://www.sip-scootershop.com/en/product/spacer-gear-box-th-2-0mm-sip_87360000


https://www.sip-scootershop.com/en/product/gear-cog-42-teeth-piaggio-2nd-gear-px-old-px-lusso_15280500

I'm not clear exactly what the problem is. Are you having trouble shifting from 3rd to 4th when you're riding, or is it only a problem on the bench?

When the gears are properly assembled it's normal for there to be a slightly larger gap between 3rd and 4th. That can be a false neutral if the cruciform happens to land there, but normally you shift right through it.

If the shimming is out of spec (and yours is), the gearbox will be clanky. The cruciform won't align perfectly with the notches in the gears and the 3-4 gap will be even wider.

Some non-Piaggo cruiciforms are slightly too narrow and exacerbate the problem.

Get the shimming to spec. Get a Piaggio cruciform. That should take care of it.

The problem is that the cruciform is slipping between 3 and 4. My shim is 2.4mm and I still have a gap of .60mm.
The widest shim that I can find is only 2.50mm. Still not good enough to bring it into spec.

You can use more than one shim.
They come in about a dozen different thicknesses.

Two of these = 2.8mm

https://www.sip-scootershop.com/en/product/spacer-gear-box-th-1-4mm-sip_16541500

Can you post up a pic of your drive shaft (axle)?

Are you using two feeler gauges at the same time to measure the gap? Because if you only use one feeler gauge, you WILL get an incorrect reading.

I agree with SoCalGuy, I don't understand what the problem is? False neutrals exist between 3rd and 4th, even on a rebuilt motor with no visible gear wear. The question is, is it slipping in to a false neutral or are you shifting in to one?? If it keeps slipping, then you could have a spacer issue. But, usually, as was the case on my bike, it is a minor issue taken care of by a cable adjustment and ensuring to shift carefully. I had an issue once, where I had tucked my gear cable ends under my selector cover and they were binding, creating a spring like effect when in 3rd and 4th providing just enough tension to push me into neutral when shifting. Took a lightbulb moment to figure it out. I think you're overthinking things to obsess about the gear stack. Barely any wear there.

It could very well have been a cable issue. They were quite tight.
I'm trying to avoid having to put the money out for new gears. As you can see with the photos, it is still out by just under .6mm. To your question about false neutral in between three and four, when I shift into four it slips into the false neutral. I think I'll try getting two 1.4 mm shims.

Maybe mixed gears?? Measure them, you have the "old" box...

That's what I was thinking too. I don't have the original ones. I bought this as is.
I'm going to try and find somewhere where they show the thicknesses of all the gears. Any ideas?

That's my point. It is happening WHEN you shift. If your cables are too tight it doesn't give your selector any leeway to find the gear. Your gears are fine! Now that it's open, shim it to spec and close it up.

If your cables are reversed, your neutral will be between 3 and 4. Also cable tension causes what you experience. I've made both these mistakes in the past.

Easy/cheap fix. Go ride it!

Maybe look into buying a new circlip as well. Perhaps the original one has been modified a bit? It's not uncommon to either sand down the thickness of a shim washer or a circlip a tiny bit in order to get the exact clearance that is needed. Spending a couple bucks on a new clip might just be worth it to see if that's the case. I have a stack of old used OEM circlips, and they all measure out to different thicknesses.

I spoke with the guys at Scooter Mercato and they said they've never seen one that's so worn out, so I am thinking that there's a gear that is the wrong size.. They also said that the PX versions are different so I may have one of those.
I have been measuring the thicknesses and I don't see any excess wear on the gear collars. Keep in mind that this thing is 43 years old and I don't know what the history is.

FYI. These are the measurements from where the gears touch from top to bottom.
First gear 10mm
second gear 11.12mm
third gear 11.46mm
fourth gear, 9.87mm.
Total 42.45mm

They didn't try to sell you multiple shims either did they.



Hec

He did mention the 2.50mm one that would get me to .50, which is within the specs

Buy a new: 2nd gear, cruciform and 2.5mm spacer. Put it back togther and ride it.

It's not. Piaggio says 0.15mm - 0.40mm…

We know someone has been working on the gearbox in the past due to it having a second oversize shim installed. Who knows what else has been changed out?
Using the gear thickness chart posted by SaFis, measure all your gears center sections, not overall height, and compare to the chart. This will help you determine if you have mismatched gears! Another option would be to call Scooter West or Scooter Mercato and see if they can provide dimensions for the correct gears and compare that with what you have.

If you end up replacing gears, don't order your spacer until you have your new gear stack fully assembled. Then take your gear float measurement and see what your clearance looks like. You may be surprised that your 2.4 mm spacer is fine especially if the new gears are thicker than what you are replacing.

I would also highly recommend you install your axle shaft with new cruciform and no gears to verify cruciform alignment for each gear. Verify that cruciform position is centered on the wear marks on the axle shaft for each gear. Verify batwing on selector box is correct for each gear. If the cruciform doesn't line up with the wear marks, something is wrong with the gear selector box, selector rod, selector rod washer or all the above. The cruciform can be adjusted slightly towards the sector box by installing shims between the selector box and engine case. The cruciform will move by the thickness of the selector box shim. I have attached pics of this test from my build. The cruciform end was painted yellow for clarity. I hope this helps. It's important to confirm your setup is correct now that it's apart instead of just throwing parts at it.



Hec

I agree, I should at least buy a new second gear. It does look fairly beat up. I do have a new cruciform. Now that I'm doing this rebuild of the whole bike including paint, I don't want to rush this job. I would like to be confident that I've got all the right parts. I don't feel like cracking this thing open again and again.
Thanks for your advice.

Wow. Thanks Hec. Great advice. I was wondering how I would see the position of the cruciform until I saw your photos, great idea. I was talking to Scooter Mercato and normally they would give me the measurements, but their digital caliper is broken. I spent a lot of time last night searching for measurements and I couldn't find a thing. Maybe most people aren't as finicky as me. It would be so easy just to blow a lot of cash and just replace everything.

Hello to anyone with p200 gears. Can you check the thicknesses from the collar to collar to compare.
Thanks in advance.

These are the measurements from where the gears touch from top to bottom.

first gear 10mm
second gear 11.15mm
third gear 11.46mm
fourth gear, 9.87mm.
Total 42.48mm