Modern Vespa

You just saved me a few hours of obsessing over the small channel - brilliant, thank you!

I think the seal was also a victim and not the cause of this failure.

That race should be sitting 1mm off the crank web. As you can see, it's obviously...not.

In your picture showing the gouge in the cases, is that how the fly side bearing was seated when you opened it up?

What I'm seeing is a crank/cylinder that were sitting off-true. I had a very similar experience last year on my GL when I missed a bit of weld spatter on the clutch side of the case deck. I can't find my post about it, but even being maybe half a millimeter off-true was enough to cause the fly side bearing race to work its way off the crank like that and push the fly side seal out of the case.

After I dressed the spatter off and repaired all the damage, though, it was fine, and that was about a year ago now.

Hopefully that isn't too scary to contemplate, but the fact that the race was pushed off the crank like that is the key indicator.

I've also gotten into the practice of cutting a slot as well. I happen to use a carbide bit on the end of my die grinder.

If not lubrication, it could be a twisted crank. Then buy a 60mm

Ooh...yeah... Done that one, too.

Check your crank is true, for sure.

Makes total sense - no tractors desired here!

Went out to measure the gears. Starting numbers:

Input Shaft: 12/13/17/21
Driveshaft: 35/38/42/57
Primary: 65

Both look stock, and it looks like the easy options are to change the primary drive? I see the Malossi or Pollini ones, but I'm a little fuzzy as to what they actually replace?

https://www.sip-scootershop.com/en/product/gearbox-24-63-teeth-malossi_20301000

This only has 2 gears plus the primary, do I then need to get the additional 2 gears to match up to the drive gears?

This feels like I'm missing a piece of the puzzle on how everything bolts together


This is different than the "upgear" package, no?

Fear not the upgrade temptation I shall be googling away on that, thank you both!

Any starter tips for checking crank trueness?

Quick removal of the race - no problem with the bearing splitter. Definitely had some sealing compound gunk applied that came off with the race.

I did a visual check of the crank (video link) and it looks pretty straight, no hiccups / catches in the rotation and gaps remain pretty constant. I'm hesitant to pull the crank if not necessary as I still fear the reassembly.

https://youtube.com/shorts/kB2Qfa1_yPA

Re-reading your advice here CM & rethinking everything. The pictures were showing "as found" condition. After removing the race, there were no obvious signs of debris / gouging on the crank other than a rubber / silicone film that was on the back side of the race (??) and wasn't visible until the race was pulled.

Can you clarify what you suspect is off-true so I can continue investigating?

The crank itself is twisted?

Or the fly-side bearing position in the case is not aligned axially with the clutch side?

I'm not sure what can happen on these engines. But here is a rough-go at a summary so far:

The engine was put together fairly well (professionally), never really run (~50 miles from owner - who knows) but it was running lean (because of a covered oil channel toasting the bearing and shredding the oil seal) which overheated the piston / piston rings (air leak causing extreme leanness) leading to loss of compression.

But if I understand what you're saying, it may be that the race coming off of the crank-web is another clue, it doesn't quite fit that narrative and it may be a crank that is not true axially towards the fly side which put additional pressure on the bearing, working it out towards the seal, blowing it and causing the air leak, etc... Is that directionally correct?

Ok, got it - the "up gear" kits with 2 pieces are the for two separate areas - the primary gear / cush drive outer & the clutch side.

The Scooter Help explainer was invaluable here (pic) & for future google-fu

https://www.scooterhelp.com/tuning/vespa.gearing.html

Also, this calculator is the best for me to play with available options -

http://gearingcalc.free.fr/

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Edit - it looks like the best gear ratios / rpm range comes from the BGM or DRT "extreme long" kits. Anyone have experience with either of these?

https://www.scooter-center.com/en/clutch-sc-largeframe-type-cosa2/fl-for-primary-gear-bgm-pro-62/63-tooth-straight-vespa-px200-rally200-25-tooth-sc6225

https://www.sip-scootershop.com/en/product/gearbox-25-62-2-48-teeth-drt_16020200?q=62%2025%20gearing

Or for laziness sake, just moving to a 25 tooth clutch seems to get me most of the way there.

62 / 25 ratios: 11.78 / 8.01 / 5.56 / 4.24

65 / 25 ratios: 12.35 / 8.4 / 5.82 / 4.45

Can't wait to hear the wisdom / experience on this - reading past posts seems to point to very strongly held points of view


aha - you get both of these in a kit, they don't somehow magically replace the "christmas tree" setup

Crank looks like it could be twisted. The twisting is the two halves against the big end pin. There is lots on YouTube. Here is one from everyone's favourite Norwegian

Very useful, thank you! Video watched, (sort-of) absorbed and tested using a bicycle truing stand. Then again with a homemade "redneck" stand and caliper.

Appreciate you & CM taking a look and seeing what you think: https://youtube.com/shorts/IgPPC0tXpPc

Using the calipers to measure for pinch, spread and axial trueness, it appears to be dead-on from what I can tell (pictures attached).

Also, there is some bearing rub (?) on the inner side of the crank. Is this normal or a sign of improper installation? (pic)

Lastly - now that the crank is out I can get a better look at the inlet pad. It looks pretty shady, is this within spec? Or am I too used to seeing everyone's really clean engine builds on here?


Conrod side down - caliper @ 51.6

Conrod side up - same @ 51.6 (hard to read)

Seal rubbing on crank web? Doesn't seem good

This feels wrong to me - rotary pads should be smoother?

Crank doesn't look so bad now it's out. With a dial gauge it will show some error, how much though. Rubbing on the web is not great. Cranks have been changed for less reason.
Has that engine ever been on holiday to Asia? Rotary pad is not original. And not pretty. If you were to do a reed conversation, there would be few objections.

Whew - good to hear! Will try to track down a dial gauge, another reason to dive deeper into lathe machining

It is supposed to be a no-expenses-spared build by a reputable well-thought-of local builder and confirmed by him in a conversation. Giving him the benefit of the doubt, maybe the PO didn't want to spend to fix the bodgey previous repair?

Debating on shelving this one and just tuning the original VBA 150 motor. With a crank, cylinder / piston and gearing changes, the p200 motor is looking to take as much $$ to get on the road as the original. Maybe I just get this one back to light-duty running with a new piston & seals and save it for a future around-town scoot. At least the rotary pad looks decent on that one

Looks like there was some welding on the rotary pad that didn't hold. There looks to be extra material where the crank web fits. I have a VBC engine case that has a similar fix, though it was a much better job. Welders and machinists who could do that kind of work were much more common in the US at one time…some more skilled than others. We associate that kind of work with SEA. Some of it can be pretty good.

Yes, that case is a candidate for a reed valve. If it were mine, I would give it a try because I couldn't make it worse. JB weld is probably not great for replacing chunks and that pad looks like it might shed some more. Welded metal appears bonded to the old pad but not to the case.

Is that the "no expenses spared" engine from CL?
Al did the rotary pad repair and small world if so.
I took a pic of one of mine before an epoxy repair. Looked worse in the photo vs in person, and worse than your photo.

Some "if I were you*"
*This is just what I'd do vs advice.

Return the kit. A kit isn't needed for what you want.
New set of rings and see how it goes.

24 tooth(helical) Cosa2 clutch for a 65 primary. Should get you close on 8's without any other gearing changes.

Check/true the crank* with a dial indicator, following the video Jack221 posted. It's fun to do. Inspect/replace the main bearing. Upgrade the seals.
*That scoring is from a metal seal that slipped out in it's history.

Electronic (DC) ignition kit.

Ha - yep! I spent some time talking with the PO & also with Al This is perfect and very helpful at the moment - thank you both! I will continue to formulate the plan and post here before I get too carried away

How carried away do you want to get here? Because you have options, some of them tame and some of them...less so...

Says the Wild Child of the bunch!

My heart says all the way. My wallet says slow your roll


Thinking about performance priorities and re-evaluating after learnings so far. Creating a spreadsheet now (that I will need all y'all's help fine-tuning) on the pros / cons of both paths.

Okay...so here we go...in order of Extreme-ness, from least to most...

1) Take a shot at fixing the pad with JBWeld. We've discussed it above. I've done it on worse-looking pads than that and those motors ran for 10+ years without rotary pad issues.
Pros: Almost free; will almost certainly work; Nothing changes
Cons: Underlying rotary may break loose; Harassment by anti-JBWeld partisans; lingering fear of eventual pad separation/failure

2) Try an in-line reed block (see Wrecked rotary fix. Anyone tried these?)
Pros: Minimally invasive; Just needs a flowed crank
Cons: Questions about how well/if it works, plus how much modification is required

3) RD-350 Reed block -- Install a little more serious reed block. This is a basic manifold. How much benefit you're looking for is (in theory) a function of how much of the cases you're willing to grind out for intake flow. Reality is that this is just one upgrade in a long series, which can be super-fun, but also will probably leave a trail of destruction as you make mistakes, learn (at least in theory), and push parts past their limits.
Pros: Fast, fun bikes; challenging engineering problems; Builds useful Life Skills like "hiding deliveries from your Signifcant Other"
Cons: Cost (will need a side draft carb, too); Probably will lead to at least a new crank, upped gearing; Risk of death going 70 on 8"s; May lead to addictive, speed-seeking behaviors; Did I mention cost already?

Extremely helpful and gives me confidence in my research as well. Thank you!

Option 1) I do not like, reminds me of my childhood redneck wrenching days. Works, but will most likely need to redo all the effort in a short time and costs more in the long-run than the better solution. I am more than a bit leary of correct case fixing after reading Charlieman's saga / mill purchase.

My take at the moment is: If the crank needs to be replaced, then reed isn't that much more expensive (slippery slope but :shrug:). That leaves 2 & 3

This means crank trueness is the guiding light. I just took a baseline measurement using the dial guage and it looks like you and jack are insanely eagle-eyed. The crank is off by 0.0025in / 0.0636mm

Baseline video here - https://youtube.com/shorts/tpyGRClYdYg

I am now going to go hit my crank with a mallet because some guys on the internet told me to follow some Norwegian guy's basement video. The scooter world is a strange place


I jest, but this is insanely helpful

I see nothing wrong with this plan.

But if you decide you need a new crank...we will talk...

And it worked! - maybe I'm the luckiest guy in the world, but 2 solid whacks as described by aforementioned Norwegian basement guru and the crank is completely true

https://youtube.com/shorts/j1vA9uC25_M

Holy smokes, very cool, you all are amazing!

This quick fix does put Option 1 - jb welding / smearing - back on the table.

You're good at this. Crank is now straighter than a new one.

Option 1, unless your partner's birthday is in 2024.
2 and 3 are cans of worm$.

Dig into the archives to see how to do it correctly, using SocalGuy in your search.

I still can't believe you and CM spotted it!

For my curiosity, I had a look at a service manual that a MV member posted:

http://oopsclunkthud.com/Vespa_service_manual/Pages/227.html

Not sure about the P200, but the VBA / VBB would have been in-spec (pic).

Crank is carefully set aside and the JB welded pad is curing. This episode still has me re-thinking original VBA motor vs P200 upgrade...


Vespa crank truing - in spec up to .003in