Modern Vespa

It is not a complete lump but it should be a nice winter project. Like we get much of a winter here in CA.

The plan is to gear it for 8" wheels and install it in my VNB.

It is missing the primary gear, input shaft, X-mas tree , clutch and stator plate.

I'll have to change the rear brake too.


A real ugly box arrived today.

What I got

very dirty but it has 3 ports

Oh crap. The cylinder did not survive the trip


Last edited by FNG on Thu, 03 Jun 2021 04:34:44 +0000; edited 1 time

PLEASE post a lot of pics from the rebuild! I am going to do the same engine this winter, and it's my first rebuild...

I posted a decent number of pictures when I rebuilt my Sprint V motor,but I also hot-rodded it, which is a lot of the thread.

I rebuilt it again a couple weeks ago, but took no pictures. I'll keep an eye on this thread and if you have any questions, feel free to PM me. Same offer to you, DD_VES.

These motors are really incredibly simple and elegant to work on, but there are still a few tricks that you'll want to know along the way, mostly having to do with when & how to apply heat rather than force (e.g. anything involving bearing removal or insertion).

My first rebuild was my VBB, and other than some stuck parts that i didn't have specialty tools for yet (rear hub castle nut, I'm looking at you... ), even that was pretty straightforward.

I'm digging your overall 8" plan. Just make sure you get the right gearing. I have the SIP 10"->8" rear hub/brake conversion kit on a Stella motor in my VBB now and that part of it works great but the gearing & power band make it not fun to ride, so it's been gathering dust in line behind other projects.

Thanks!
I'm waiting for the paperwork before starting any serious work, but when the time will be there I will ask!

Nice score and great plan. A Sprint V engine geared for 8's is pure joy. It's going to put a big smile on your face.

If you build it out with a torquey top end like a BGM or Polini 177, you'll get the sort of nice wide powerband that really bring out the fun of 8" bikes. Lotta torque, not a lotta shift, just lots of maneuvering

Biggest problem you'll probably run into is finding a good exhaust that doesn't drag the ground on bumps and tight turns.

I also have documented my Sprint 150 rebuild. Check it out as it may give you a different view.
http://modernvespa.com/forum/post2269198

You're lucky only the cylinder broke! Glad it is otherwise OK. That does not look like a safe shipping method.

ph0ngvu's rebuild pictures raise a great point...the Sprint V motor came with two different cranks and main bearing/seal configurations.

Some of them had a small taper on the flywheel side, where others had a P-style taper.

You have to look at the clutch-side seal/bearing to see which one you have.

ph0ngvu has the older bearing setup with the main clutch bearing inside the crank case. I have the newer version where the main bearing sits on the clutch side of the seal.

This determines which seals you need, along with the order of assembly and re-assembly order (seal->bearing->crank vs. bearing->seal->crank)

When I replaced the crank I put a P-taper flywheel in it so I could use the SIP Vape variable timing ignition.

Looks like a fun one for "winter"
I happen to have my VBB split right now - so some of this is also fresh for me:

Appears to be the older case to me - with the clutch side seal on the outside. The bearing still being on the crank - and the blue seal showing in the motor half.

Crank's are kinda surprisingly cheap - and you will have options of either updated ones with PX taper on fly side, or std - should you decide to replace.

In any event - the good news is, the SIP vape is also now available in both sizes of taper (I think when Chandlerman did his, he was an early adopter) so once you determine what crank you are using - you can still go with it either way - if you wanna.

SIP catalog has some nice info on the gear set ups and options, including the original xmas tree sizes.

https://www.sip-scootershop.com/files/catalogue/index.html#/485

And if you want to consider some custom options - this is a pretty cool tool. Swipe right after entering the gears to enter the tire size.

http://gearingcalc.free.fr

I think I had the first SIP/Vape Ignition within this forum, although the GSF guys were miles ahead of me, of course. That was on my Stella, but I have generally been pretty impressed with it other than issued I have continued to track in my thread about it, namely poor quality copper wiring on the CDI.

I replaced my Sprint small-end crank with a PX taper for long-term flexibility on ignition options, as well as compatibility with my other bikes (other than the VBB, but it's a 2-port motor, so no point in trying to hotrod it too much).

That original 6v points AC ignition now lives with SoCalGuy to keep his Super's ignition burbling and his lights suitably dim

One of the first thread's I read. Was pretty cutting edge move at the time. Ha! I think someone will have to rip those point's from his cold dead hands before he swaps them for electronic ignition! (morbid image of SoCal lying in state in open coffin - gripping points and stator - just ever so Mona Lisa wry smile showing on his face).

BTW - got a little insight last week from inside the walls at SIP.
Here's the scoop.
They have a new CDI coming out in about 3 months - will have 5 or so pre-programmed curves on it.
Realize other's have been there already - but suspect the VAPE made product will be reliable - perhaps give kytronic a run for their money.

Some of the curves will be more mid RPM friendly - I'll post a bit about it on my thread when I get there.

Do you have a gearing recommendation?

I was going to build it up with the stock 150cc cylinder but since it is broken...
Maybe the Polini 177

OOOOOOOOOOHHHHHHHH!

Well, I guess I know what I'll be getting myself for Christmas THIS year.

Did they say if it will it be a CDI swap-out with the existing Vape stator, or a whole new kit?

Swap out CDI. Plug and play with existing stator.

FNG - you are barking up the right tree with SoCal - he runs 8" and the Polini so that is pretty well as good as you could get for gearing targets for where you are going.

I did this to AnaKey, but that was while it was still in the motor!
High speed/rev seize

Why yes, as a matter of fact:

Primary: 22/67 (3.05) or 23/67 (2.91) for touring
Input: 13, 17, 22, 27
Output: 57, 52, 48, 42

Do you have a gearing recommendation?[/quote]

Why yes, as a matter of fact:

Primary: 22/67 (3.05) or 23/67 (2.91) for touring
Input: 13, 17, 22, 27
Output: 57, 52, 48, 42[/quote]

Thanks SoCalGuy. That's good information.

I had a little time to go out to my shed (workshop) and check out the engine.
I did a little cleaning and took some more photos.[/i]


Cleaned off some of the crud.

My case is the type with the main clutch bearing inside crankcase.

It looks like the ports have been opened up some.

A little blob of JB Weld where the port was opened a little too much.

More shipping damage or is there a reason why someone would do this?

How can I identify this crank. Is it worth using.

Crank is old style (assume 57mm stroke) with narrow taper, but the oil seal arrangement had already given us this clue. This limits you to points ignition or aftermarket electronic/12v conversion if you so choose. A few of us have used the SIP/Mazz conversion crank that allows the use of the stock PX 12v electronic ignition.

The condition of the crank is hard to assess. Judging by some of the damage and the evidence of porting, I'd say that it could have had a hard life. If it were me, i'd replace the crank. It's possible that it is aftermarket, possibly a 'sports' crank to go with the porting work. If so, then it will be much newer than the motor and therefore could be an asset to you.

BTW, the photo of the flywheel side shows what looks like a crack at 6 o'clock. I would want to investigate further and repair. Having said that, I'd be considering a different set of cases at this stage, although my personal preferences can be ignored

Looks like several possible spots where Bad Things might have happened with these cases You'll definitely need to investigate those further.

For the chip in the ring around the stator, I'm going to guess someone used a gear puller to remove the flywheel, based on recent personal experience.

I had my flywheel stick to the crank tightly enough that I destroyed two flywheel pullers trying to get it off. Ultimately, I had to use a 3-armed gear puller to remove it, but along the way, it dented that ring. When I tried to tap it back into shape, it broke pretty much exactly like that.

As to the crank, my stock crank is marked with the Piaggio logo. Mine is also marked as "3760/S". That one looks to new to be stock to me.


:cry:?

Legit Vespa

I'll investigate further.
I'd hate to abandon these cases as I haven't seen many for sale. Fortunately I don't have much $ in them.

After further inspection, it appears to be a crack.

It looks like I'm back to looking for a set of cases for my VNB.
If you know of some for sale.




This looks like a crack to me.

Bummer!

Yeah it sucks but I did get to waste several work hours shopping on the SIP website. 😁

The seller gave me a refund.

I'm back on the hunt for a engine.
I'm looking for 2 or 3 port 4 speed.
If you know of something PM me

I have the original 2port motor out of my VBB that's not getting much use these days. Hadn't really thought about unloading it, since no one seems to want a 2-port motor, but it has a Pinasco 177 on it and is unmolested other than a little bit of intake to airbox matching and a 20/20 carb.

That sounds like it would be fun in my VNB.
If you decide can part with it PM me a price.

Are you sure? It doesn't look like it extends all the way to the edge of the bore where the seal is. You would expect a crack to do that. And it doesn't extend to the bolt hole either. Again, very odd behaviour for a crack.

What does it look like from the other side?

It'd be worth a good look at with a magnifying glass and a decent light source to make sure. From my experience, looking at that photo, it doesn't look like a crack to me, rather a casting imperfection.

Just my 2 cents

Lemme think on it and I'll PM you if I decide to let it go.

You are right in that it doesn't extend to the seal or bolt hole. It is also not visible on the other side of the case.

If I build this thing and that is a crack what problems would it cause?

Smart man. This is a casting ARTIFACT, not so much a defect, I believe.
This was cast by the permanent mold process in an iron mold, one of hundreds or thousands of such molds used until they were finally too cracked or warped or patched up, so they grabbed a new mold and scrapped the old. These seams or lines are called "finning" for obvious reasons and happen when a crack is still young enough to be tolerated, but fills with a bit of molten aluminum as seen here. I had a set of cases cast from a musta been virginal mold set once, and they were flawless, and 100% seamless with no wrinkles and just bootiful to behold!


another to the left and the one near the bore would show crack on that machined surface if was a crack

awesome! get that thing together!

I think V oodoo has it right.
Molds wear - and the seams between the mold parts get banged up from handling and cleaning between moldings.
Easy way to tell.
If it is in fact a parting line between the molds, it will be a raised "fin" as Terry notes.
If it is a crack - it won't be raised.
Grab a magnifying glass/flashlight/ and something sharp to run over it like a sharp awl or toothpick.
You will likely be able to tell if it is a raised fin or a separation on two sides of. a crack.

Good luck!

Hello again. I haven't posted anything in long time.
I have been stopping by regularly to see what you guys are up to and to learn some things.

During my absence I had Gickspeed fix the hole in the transfer port that someone had smeared JB Weld over.
While Jonathan had the case he matched it to a VMC 177 cylinder kit and built the engine up with all the fancy bits that I've been dreaming about and saving for.

I just installed it in my VNB. Everything is going smoothly except for the exhaust.
The Polini box is hitting the center stand.
Is there anything I can do about that? Can I just grind off part of the center stand?

Thanks for your help.

Had the same problem. Polini says the box "will fit on 8" bikes" ... which is a little misleading. Yes, it fits, but fouls the center stand. Same with the BGM. Get a side stand.

A MRP main stand offset from SIP would solve the problem of exhaust hitting center stand.

I was surprised that my Bgm Touring exhaust fit with very little problems. I did find out last night with my wife on the back there's not a lot of clear for those leany corners got a nice scrape in the muffler. It's fine when I'm alone but two up I need to watch.

Thanks socalguy & rowdyc for the suggestions.
Both of those are better than me taking a grinder to my center stand.

I did a little bit of searching today and haven't found either in stock in the US yet (still some places to look). So maybe I'll go sans center stand while waiting for one to arrive.
Maybe I can fit a block of wood in the cowl to use as a stand if I stop somewhere.

My SIP Road 2 fits nicely but I haven't gone 2up with it yet.