Modern Vespa

Smoke found a tiny leak at the cylinder base gasket for me on the white Stella just last week. It was like an inch-long gray arrow pointing right at the problem spot.

The mystery deepens then…

Thanks guys.

I suspect it's the area of "oil sucker" thinness - and I'll explain why - after I test.

What was you pipet test?

Ah I meant using a dropper/pipette with soapy water to find leaks instead of using a spray bottle. Spraying soapy water naturally creates bubbles.

paint brush works as well.

Appreciate everyone leaning in and giving best tips and tricks.
I've sprayed it, droppered it, brushed it, and smoked it.
Im higher than Tommy Chong - but there is no evident leak.

Pulled the fly wheel off - retorqued the center bolts.
Used all above methods and found nothing on that side.
Clutch side is a bear to get to - if I go there - I'm just gonna pull the engine.
The leak is sooo slow.
WTF?

To test clutch side - I rigged up my own set of new tests.
1. I created a fitting for the crank case breather hole - so I could attach a rubber tube to it. Then I put that tube in some very shallow water. Not so much as a pin sized bubble came out when I pressurized the case.
2. I then took a second pressure bulb - attached it to that tube - and pressurized the crankcase. This time - I watched the other pressure gauge to see if any pressure from outside could get in. Again - not the slightest.
Idk - tests seam to show its not coming from the cases.
Just seeps out so slowly - maybe I should get a new o ring for the test equipment...
Not sure what to make of it.

That's a bummer that it's still a ghost.

You're one step away from dunking the engine in a tank of water.

Joking aside.

That's still a pretty good leak the speed that it's going at.

With the gearbox side test, it'll take a quite a while before bubbles appear because the leak is so small for air to be pushed out after filling such a large space.

Maybe a leak with the pump/gauge equipment?

I usually use a finger over the hose/adaptor/gauge to make sure those are airtight before fitting it to the engine.

Stumped.

Purpose of gear case breather test was to try and expose a leak without pulling wheel, clutch cover, etc.
If they come off - its going to be with the motor out on the table.

I can't rule out clutch side leak - but if it exists - it is very slow.
Ha! That leak speed seems very slow to me.
Sounds like you have experience of that level of leak being significant to operation.

As aggressively as I pumped air into the crank case - I would have thought it enough to at least make the gauge connected to the inner volume, blip - even just a hair.
There was nothing.

I'll focus in on the head next.
Test equipment appears to be ok - but will have to devise a better test to ensure there's nothing weird happening with it.

That's a good point, a leak that slow, you'd wonder where in the running would it affect jetting/temps?

But the speed of this leak, I'd still be looking for it for peace of mind.

Red PX
https://youtube.com/shorts/cDOwZG_8LIg?si=_KnalBB38oQnrTJj

The leak here on this red 210 still ran. 90% certain it's clutch seal leak. The owner didn't want to deal with it, even after all the red flags it means. The power was terrible, but didn't over heat because jetting took care of it. Ridable, but not much better than a stock bike.

Black largeframe
https://youtube.com/shorts/HWtohp6NSHI?si=4mvGQRobPSuC3JMv

This one seems about the same speed as yours, intake manifold leak.

Egig170
https://youtube.com/shorts/md0Nwc7YOLg?si=kmhv6JeDQ1RC9fOi

For my own engines (this is on the egig engine), zero needle movement. At least you know it's rock solid and any jetting is reliable.

Did you remember to cut the gasket nibs?!?! Longshot.

IIRC, you sealed the living shit out of your case halves with hondabond or some such, so probably not the issue, but cutting the nibs off the case gasket helped on the Spanish.

I cut the nibs off at birth - it's more a hygiene thing than religious.

I've been thinking of your hunt to find the leak.
I'll go at it one more time with it in the scoot - then decide if it's worth pulling motor for at this point or just ignore it until it gets cold and rainy out.

Well - it's been 5 yrs and 100 pages.
For regular readers of this thread - consider: You will never get that back.
¯\_(ツ)_/¯

For my 100th page extravaganza, I decided to pull the motor - and track down my mystery leak.
This one's been weird.
Sometimes it runs without trouble.
Sometimes it gets all air leaky.
Air leak test confirmed - but have not been able to track down the source.

Given the mods that occurred circa page 76, it was anyone's guess.
Some cracking of an internal weld?
Porosity through the added material?
A worn out seal?

I only have 3Kish miles on it - so with ego a little battered - I pulled the motor and put it under 5LBs of pressure to see what's what.
- Crank remained positioned: tight as a drum on both side and top of my L shaped inlet.
- Pulled the clutch (could hardly remember how) and used a CM method for testing by covering in oil. Not a peep.
- Was just about to pull the fly wheel when the exhaust cork came free - so I used a dead blow to tap it back in.

That's when the leak tester stopped loosing pressure.
Gave the exhaust stub a wiggle - and the leak re-appeared.
WTH?

So leak found. Perhaps stub has worn itself a little loose - or design is just not that good.
The O ring being on the OD of the stub has to be very low profile.
Otherwise - you couldn't get it in the outlet of the cylinder.
But that means it doesn't get a lot of compression.
By moving the O ring to the face, I can control it's compression % nicely.
So I did - and everything is better over at Casa CM!
Ha! - wife wanted to know why I was in such a good mood last night.
https://youtube.com/shorts/JJu-baEFUMM?feature=share

Good sorting. Nice to see the unicorn getting some love.

CM2 doesn't mess around when it comes to fixing stuff.

"Badly engineered? Not any more!"

And we all lived happily ever after.

Yaaaasss!

Win!

Persistency pays off.

Now the question is: what's next.
Split cases anyway - and add some fangs to the beast by flowing crank and increasing inlet timings - or - button her up and rework the sidecar frame.

I built it as a learn to weld project.
Thought it would be good enough to prove out the concept.
Could do much nicer.
- 30-40 lbs lighter?
- Easier to fine tune alignment?
- Hydrologic brake that is balanced with front caliper…

Kinda leaning (🙂) towards sidecar project.

You know you've totally ruined any chances of me owning a "normal" sidecar after the geometric wizardry you've created with the Orange Unicorn.

So if you asked me, I'd say side car cleanup too, and maybe make three or four frame setups to sell to your MV homies with sidecars

I say go with the sidecar project.

You're into the "high risk, minimal return" portion of the tuning game at this point, whereas getting fifty pounds of weight reduction, plus improved weight distribution and handling will give you a much more appreciable boost than a 5% power gain.

Vote for sidecar upgrades…

Engine seems to be in a good place, doubt any extra work will be any fun to you.

Side Car!

Awesome.
Only took 100 pages to get buy-in.

Have some travel that has to occur first.
Will order some basic tune up parts for the scoot and start collecting my light weight frame ideas.

Should be a fun one.

Driven side car wheel would be cool though likely unworkable due to the need for a differential.

Equalean inspiration: https://www.bike-urious.com/leaning-hack-1981-equalean-sidecar/

Given the Vespa frame follows the aircraft stressed skin approach, maybe the sidecar could be a chromoly spaceframe

My kids would murder me if I didn't get in on a leaner sidecar frame…

Leave The Unicorn alone.

It's a legend in its own right.

Did John Harrison "tweak" H1, his brilliant first Longitude Clock?

Did he add better brakes or make it easier to align?

No! He built H2, H3, and finally H4!

Like Harrison's clock, the first iteration of The Unicorn should be preserved as a monument to its creator's ingenuity and proof-of-concept.

Besides, you have that wide body frame to mess with.

Socal... makes an argument. *nods slowly*

I'd also like to see what you have in store for your wideframe project.

Sidecar. You have plenty of motors left in you, it's actually not necessary to stick to just one.

Also (once you put aside the obsession with rotary valve) reed will give you much more scope for power. However, I do acknowledge that you prefer to do things the hard way.
As an aside, a rotary disc would be a big challenge for your skills and give you an opportunity to create discs with custom and controlled intake timings. Think BFA did a smallie one with a toothed drive belt. That thing looks like a fairground ride!

Space frame would be good. And given that the sidecar only ever seems to carry stuffed toys and beer (though not necessarily in that order), there's no need for the bodywork to be metal. Carbon fibre sound like enough difficulty for you CM?

Forgot about that guy…

There was a box...just sayin'...

I have always thought it would be cool to have a GP style side hack on the street. If you ever need a monkey for ballast, I'm in.

Not quite a vote for sidecar, although that would be good. But could you build one of those bubble scooters like in that AI picture of them all on the bridge.

Range of responses caused a good chuckle - and allows me to sharpen my perspective.

On Rotary: I think I can get = or > reed
On reed: another failure point that sounds weird when it's working. I'm a traditionalist. 🙂

addition of 10-15 degrees of inlet timing (at 15mm of width) and some crank flowing… must be 2 or 5HP? and 1500RPM more band if I want it?

On a certain Arizona box. Oof. I feel guilty.

On an additional motor and making things difficult… first was difficult.
Next would be much easier.
Have a recipe now.
Second motor should get built.

On space frame: plan is something like that. Sketches to follow.
Jump in with some critique!

On scooter body: below is the inspiration. Think airstream construction. (Phase ii after frame)

On first proto: more bothered by my ugly workmanship than the design. It should be replaced.

On wide frame. Have to perfect my design - then build the wireframes…

Fixed that for you. That's lucky!

the super early MotoBi Spring Lasting 200 had a setup like that, then they switched to piston port.

Trabant did too.

Ginch - thanks for the "fix"... and the trouble...

Motor appears to have significant life left in it - so think I will give the upgraded frame my focus.

Tho the sidecar wheel aligns with scooter's rear - I want to tie the brake in to my front caliper.

When I ride now, I can use my rear break to set up for corners.
It's not squirmy or weird.
Feels totally natural.

When I get on the front break - hard/quick - I can feel the weight of the sidecar more.
I think having having it tied to my front brake might be nice.
I can always remove if not.

Starting to collect parts.
Safis - if you are reading - can you help me identify the Aliexpress brake line that you used?
I think they sell something I can make compatible with my SIP 5mm brake line.

Here is an example of what I see.
Am sure I saw Safis utilize something like this on one of his projects.

I have to go back and reread your epic thread. The rotary repair and casework is brilliant. I would be great if you offered that as a service. These cases are damn near bulletproof, but the rotary pad seems like a fragile weak link. It's one of the reasons I chose a Malossi reed case instead of rotary. DIY machining has tempted me, but I can only go down so many rabbit holes.

Sidecar. I was thinking doped fabric like a Sopwith Camel. When I built my flight sim cockpit, I used a router on the end of long compass arm to cut curved ribs out of plywood. The skin was glued strips of Baltic birch. This would probably be really heavy for a sidecar. I thought of using this idea to build a snail camper with a bus cab and frame. Curved rather than square camper body. Subaru engine. Sigh…

I use AN3 line and banjos. Depending the project I also have a shop close by that does pressed fittings...

Hose...
https://www.aliexpress.com/item/4000181690135.html

Banjos...
https://www.aliexpress.com/item/4000311237686.html

Piling on, it seems the decision has already been made but if the engine power is already serving your needs, definitely go to work on the hack. Hydro brakes sound good, but for me, I would not try to reinvent the sidecar itself. Rather, get this one where you want it and pick up a P200 to start another hack project. With all you learned from this one, starting a new one from scratch might be the way to go. And another 100 pages of reading and entertainment for a fool like me.

AN-4 push-lock hose from Summit or Jegs is rated for use with E85, so should not harden with the E10.

I am in the process of trying it out on my Rally.

Edit: talking fuel line here, not brakes.