Modern Vespa

I've been a long time reader, not-so-long poster here, but having finally started to settle into my house after leaving Brooklyn and the insanely expensive 1 car garage I was renting that was 2 miles from my apartment, I have started to put together my plan for the 1976 50R I picked up close to 2 years ago, from a friend in Atlanta.

I had been looking for a small frame project in New England, but as I am sure many of you know the NYC Metro area commands a huge price tag on vintage motor-anything.

Either way: enough back story. My plan for this bike is to build this slightly thrashed bike into an all-occasions rider. I want something with enough grunt to handle rural Connecticut roads without feeling too burdensome (I have a garage full of mopeds for that purpose) but is also small enough that I can load it onto the rack on my SUV and bring it to NYC and enjoy there while I work.

I'm going to start solely with my plans for the motor, and hopefully everyone can weigh in, and correct any issues you might see. I have built a number of Vespa mopeds, and motorcycles, but as it usually goes my experience with smallframes is light.

1) I am going with a new roller 51mm crank in order to run the larger cylinders. I may be able to eek the same power from the shorter stroke, but I have enough 10k revving mopeds and would like to make this torquey over peak power. I would prefer to stay 19/20 so that way I can keep the stock points for now. I know, POINTS. But I find points to be incredibly durable and field-serviceable. Should budget allow, I could see myself going with a simple static CDI system in the future.

2) My plan was to mate this to the 57mm DR Cast Iron kit. I've used DR's on my Vespa Mopeds and enjoyed them, and have heard that the DR is a milder cylinder. And I COMPLETELY open to other suggestions. My experience in moped cylinders also extends to just about every other major brand, so please: tell me your thoughts.

3) My plan was to remain as a 3 speed, as I enjoy my Lambretta's 3 speed gearing and ride style. Mostly though, this is to save some money as I know gearsets are something that shouldn't really be nickle-and-dimed. Along these lines, I need to consider what primary gears I would need. I am hoping for a sustainable 50-55 on the flats, with a standard sized rider.

4) As I am hoping for plenty of torque, I realize the clutch will need addressing. I have no clue where to start on this, except I see alot of information regarding swapping to a PK style clutch. I am happy to get some links to pertinent information, but if there is a modded stock EQ or drop-in solution that will work for my plans, I am all ears.

5) For pipe and carb, I have a spare PHBL 25, PWK28 and a handful of PHBG and Mikuni, but I wouldn't mind using the PHBL to keep the carburation Italian. For pipe, I was looking at the EGIG Banana, but am happy to consider a traditional cone pipe that won't break the bank.

Once I can start putting together the parts list I need to get the motor squared away, I will start looking at freshening the brakes and suspension to match, and then finally get the seat recovered and some fresh cables installed.

Looking forward to any advice and help, as well as getting further into the build process.

Nice bike! Looks to be the same frame as my '79 v100.

I'm sure you know from your other 3 speeds that first and second are pretty damn useless especially once you tune that thing. I'm kinda in the same boat.. want to upgrade to 4 speed but don't want to cheap out on it, and the pricing gap is pretty big between good and cheap.

Curious to see how the DR turns out. It's been suggested to me by greasy, but I had originally been planning on the vmc kit, but have been irrationally considering the egig 170 kit for it instead!

Looking forward to following this and seeing how it turns out.

Good one. It'll be neat!
I'd suggest doing the tryes, brakes, and shocks etc. first.
Fix all the little rattles & niggles like new cables, stand feet, and seat cover etc. Ride it round a bit so you get a feel for it and how far you feel comfortable going with adding extra power onto the above.
I know on my old 1960s 150 that the standard engine is about right for those old drums and front shock.
All the best with it and looking forward to seeing some pics.
Cheerio,
P

you have a 50, so at best you're looking at a 80~102 kit. the gearing is shit. while you've got 4 cogs, the primary is wayyyy to short to be useful.

so you gotta crack it to do primaries? then do the crank and you can then run anything you wants. bump it with a 19~24 carb and throw a noisemaker at it.

if you really wanna party, get a decent crank so that you've got more intake timing. and that you can upgrade in the future. and then drop dough for a decent EI set up.

I would normally have done this, but I have been wanting to build a smallie for a long time now, and I already have a good handful of 50cc bikes that do 30mph (and a handful of "50cc" bikes that do 55 lol).

And I completely hear you on chassis upgrades. I know that I am going to want them at some point.

I considered the short stroke crank cylinder options, but given that this is a brass bushing crank and I KNOW I wanted a fresh needle bearing crank if I was going to rebuild, the 51mm is just what makes sense. I was going to go with the standard Mazzi crank, but if you have a better suggestion, I am willing to tap a little more fundage in there.

Appreciate the advice all around. I am not trying to do a full race build, but having something I know I can grow and add to is important as well.

You have the primary 'granny gears' on your crank and clutch basket that come on all 50s I think. Nice, coz you can pull a plow in first if you need to but you'll never see 50 no matter how strong you build the motor with those. I like the 90/100 primaries on my mildly hopped up 125 smallies, 50mph is easy and pretty quick. For higher top speed use the Primavera 125 primaries which go faster but get there too slowly for me w/ just mild tune Or you can go cu$tom gears. Anyway, 50 is fast enough for me on my smallies and I love getting there real quick.

Note: I have no idea how your smaller 9" tires play into this, taller Primavera primaries could be ideal.

This is HYPER helpful information. Looking at the calculator I know that to reach 50 with my current gearing I'd have to push 9k rpm, which is not alot for most of the other 2t bikes I ride, but not really the "touring" type build I am aiming after.

I will set my sites on the Primavera gears, which I think (with some quick maths) will lead to a VERY similar final drive to a 10" wheel bike with the shorter
90/100 gears.

Excellent, that's one facet I can add to cart.

V90 or 100 gears are great for where you probably want to be. 125's with the 9's would probably be ideal, depending on the tune.

If you don't have the R's or the CC's to push the long legs, err toward the 90/100

Either way, highly recommend a short 4th tree.

I can see the merit in aiming for 90/100 primary, now that I think about it. If I run the shorter 90/100 gears and find the primary gear limiting, I can easily convert to a 10" rim, gain back the gearing that way and also set myself up for future brake upgrades.

As far as the short 4th, I guess I will have to price-out the 4 speed conversion. While I certainly don't mind a 3 speed, if it doesn't make sense to re-split the cases should I need/want the fourth, then maybe doing it all at once is the smarter option, even if that means that I have to wait a bit longer to acquire the funds.

Hoping this week I will get to continue the motor tear down in anticipation for getting parts in. I have to juggle this with trying to do a seal replacement and leakdown test on my Derbi Variant for a ride next weekend, and taking care of my newborn, but I think I can manage that.

remember, the good money spends once.

half stepping it yields a mediocre finished product.

like, you could go with a DR, it's fine. perfectly useable top end. but a polini is only $75 more. you can stay with a stock pipe, but a cool banana is only $50 more and rides soooo much better. you can stay with a stock 19 setup, but by the time you buy that you could've spent $50 more and gotten a CP21 instead.

to me, building the bottom end out right and then adding the pieces that will complement where you're trying to go is the key. do all the kick ass stuff down town, then add a carb and a decent pipe. that way, down the line if you wanna go whole hog you don't have change anything but your top end!

either way, you're going to have to change up your gearing.

I think you gotta settle your wheels and tires before you go too deep into the gears. The difference in circumference has got to be significant.

If you can find good new tires and like how they feel, you may be better off w/ the taller Primmy gears. If you think you want to go tens before long for bigger brakes as well as rubber, then the 90/100 set might be more fun UNLESS you build some kind of monster.

This is the advice that I needed to hear honestly. I will plan on going harder on the bottom end build. Primary gear ratio is easily tackled, but the hang up in my mind is whether or not I convert to 4 speed.

I really havent delved into the process, or researched if the standard, CIF gearsets are a good investment. I already know that I am happy with the 3spd feel from my Lambretta, so I am hesitant to convert even though I "think" I should go 4 speed to avoid doing things twice.

lots of choices and planning to do.

I've found a few places that have stock in the 9" tires, so for now I am going to stick to that format for now.

Current cart is going to include bottom end items to get the bottom end rebuilt, thats my first step.

I've always been a proponent of using quality components that match up very well together in order to have the best reliability and best ride. If you install a tuned 130cc top end on a stock clutch, well you'll probably have a bunch of clutch slip. With a 3 speed gearbox you'll have have to contend with having a wide ratio transmission that will have difficulty climbing hills. An EGIG Banana might not even play well with whatever crankshaft and cylinder port timings that you are after. A hopped up engine can be dialed in to be more reliable with a variable timing kit. Adding up all the various parts and pieces to have a reliable (and well matched components) you're probably in the $3~3.5k+ range. Yes it can be done for less, but it will probably be a bigger headache when it comes to fixing and replacing the inadequate parts. If you're looking for 50+ mph, what about just finding a used stock 125cc top end, crank, 4 speed tranny, clutch, stator, carb? All those parts together would be uber reliable.

If you could just find a Primavera 125 motor for a grand or so, then a 10" front hub conversion and you'd be all set. Anybody holding?
( I have a spare 10" wheel, 4 speed smallie motor, but has 50 crank and Polini 105 top end - maybe good for racing, but no fun just riding around.)

I agree that a stock 125 motor in this frame would probably solve a lot of issues. I would consider a full transplant, but honestly finding the right motor for a decent price would be a necessity. I don't want to spend $1k+ on a complete bottom end that needs more parts and work to run, when for around that I can almost be at a similar point with the cases I currently have.

The making it reliable and tuning aspect is not something I am really worried about, I have a lot of experience working with vintage smallbore 2t bikes professionally (spent more than a few years at NYC's only brick-and-mortar moped shop).

I also do understand the common issues around the WR 3-speed gearbox and how that requires a flatter, torquier tune as compared to a 4 speed which can be a bit peakier and still maintain speed.

If I could find some folks with stock primavera gear that had upgraded or replaced, I would definitely jump on the chance to grab them. I really do appreciate the quality materials of the OEM stuff, so getting a stock 90-100/Primavera 4-speed transmission setup, and maybe even top end, would be something I would consider.


In either case, always appreciate everyone's thoughts. This site as a whole is overly gracious with offering sound advice without undue criticism, which is frankly very refreshing. I am hoping with the holiday weekend coming up, I will have the opportunity to finish the motor tear-down and see what I am working with.

kajiit house of wares has a bunch of used stuff that's mildly racy, but good used stuff. I'll start digging and see what I can come up with.

I will say though, trying to bring this in at around 1K is very ambitious. I mean, sourcing spare parts and looking for deals will knock that down a few bucks. but when bearings, seals, seals, gaskets and consumables are about 15% of that budget... then add in all the other bits and bobs at 100 here, 100 there, it adds up with the quickness.

but the thing I would 100% spend on would be:

primary gearing-- I'd source used on this V90/100 sport, primmy that somebody upgraded or lightly used race parts that somebody tried and didn't like.

4spd setup-- the CIF set is fine. hell, even the indo PL kits are ok. but if you upgrade down the line, you'll be kicking yourself that you didn't grab that short tree.

clutch-- count up and see what you've got. a few companies make gears that you can mesh with your stock basket. but at like 70 bones for a new primary it's kind of a no brainer. if you wanna go rickey racer, just remember that most of those kits take a proprietary clutch pack. you can go old school or new school on the clutch, spend a little dough or spend a whole bunch. personally, I don't think you'll be making enough power so I'd stay stock basket and then get some nice plates (ferdo, surflex, or malossi) and good springs (either the polini wave washer or the stoffi multi setup that you can install or the single uprated). I literally have a clamshell FULL of clutch parts that I'll make you a deal on.

crank-- a stocker mazz, tameni would be fine, the gas flowed mazz or SIP is about 60 more, but if down the line you're looking to get a little frisky you don't have to splash that cash. but, again, used is an option here as well but it's a little bit of a dicey proposition.

take off kits and top ends can be difficult. if you need to bore it and get a fresh piston and there's almost $200 out of pocket. while you can pick up a DR130 for 150 or a VMC or series pro for about 40 more. the benefit to those kits is that they come with a head and have updated porting. used, you might get a head, but unknown use and abuse. don't forget you'll need a shroud and studs.

stock intakes and carbs are fairly inexpensive and plentiful. take off exhausts even more so. I'd totally go used here and that's something fairly easy to swap out.

hope that helped.

now break it open and let's see what you got in there!

Honestly SUPER appreciated. I completely agree. I'm pretty used to moped motors, and especially VESPA moped motors where I can buy HQ bearings and seal (that's right, one seal) for less than $28. I'm not against spending more (if it grew on trees, I'd chop down all the trees on my property for a build), but trying to be reasonable as a newer home owner and father while still enjoying myself is what I'm aiming for. Seems like this would be an easy go, and if not it seems like one can buy a new set of any combo imaginable for under $100. I will definitely aim for getting this ASAP. That's great to know. I have used CIF for Vespa moped transmissions to good success. I'll have to look into the short fourth. Does the short fourth reduce the gap between 3/4 or give more space, giving it an OD effect? Definitely not going whole hog on the clutch for now, especially given it's a wear item I would prefer to try and get a smooth working example and look at upgrading as I get a real feel for my needs. Once I pull apart the clutch, I may take you up on those clutch parts. I definitely think the crank is something that I will spend money on. Having seen the large difference in the Ciao/Bravo/Si cranks, I won't mind spending a smidge more for gas ported. Same situation as the crank, this is something I would prefer to have new to avoid the need for honing or boring, let alone a new piston, etc. You really got me thinking on whether the DR is a good choice, when a bit more power is just a small amount more. I have the stock 16.16 from the bike, but I think 19.19 is the minimum I would want to run on this bike. I have a handful of carbs that I could use, and have built a number of intakes for other mopeds, so may give that a chance as well. As for the exhaust, I am open to anything. I obviously love a big multi-cone chamber, but understand how effect the banana style pipes are for this application. It helped immensely. I hope to get the cases split tomorrow after my half day at work.

Greasy's advice is great.

I went down this rabbit hole a few years ago building my smallframe. 50 special Small Frame rebuild advice needed
Since then it has ended up with a TM24 and a reed valve intake off the cylinder.
I had to expand my budget to $2000. It is super fun to ride. A friend ended up with the motor on his 100 Sport and was able to keep up with or surpass bigger bikes with ease.

Not sure if this will be helpful, but I think there are a few things worth considering.
1. If you are going to be riding with other scooterist in a rally or group ride setting a kitted 50 without other internal upgrades isn't going to be much fun. You really need to find a 125 motor or spend the money on this motor, dig in and make suggested upgrades.

2. A 75-105cc top end with no other internal upgrades is probably going to be slightly underwhelming, but you could have fun solo riding around town. I had a 64' V90 that was great fun to ride around town, eventually I wanted more speed, but I probably should have just kept it as it was.

3. If you plan on keeping the scooter or at least the motor spend what you can to build the motor you want. If you are likely to sell the bike at some point it is worth considering keeping tighter budget. It could be real easy to get upside down with what you spend building a tuned small frame motor vs what the bike will sell for.

4. I ran into a circlip failure on the driveshaft and had to rebuild my motor a second time. Aside from the driveshaft I only had to replace bearings/seals/gaskets(and circlips:). Catastrophic failure is always on the table.

5. A P200 may be better suited for touring and cheaper than building a smallframe.

Declan! Thanks for the advice man, always appreciate it.

I know there are better platforms for what my *desires* are, but I really love the smallie framesize and aesthetic.


A week or so ago I buckles down and started disassembly on the 50r motor. I was almost hoping it had a 50s 4-speed in there given I was getting some weird feedback on the motor ID depending on resource, but it is a 3-speed.

Everything is very clean for the age. Flywheel is the older Femsa that is supposed to have a circlip for removal (no puller threads, see photo), but taking it off carefully with a rubber mallet and some lite applied force was not a problem. Someone had been in here to replace the condenser at some point, but not much butchery which is good.

Wasn't able to access intake patch as I had to order a clutch puller (I thought my Motobecane ER3 puller would work, but the od was just too big to fit into the clutch. But judging by the crank lobe it will be fine.

So at this point I am torn between working with the 3-speed and building some with a wide flat curve, or going to 4-speed and being able to eventually run something more peaky should I want to go that route.

I know I would need the gears, cruciform, and primary, but there's also a needed output assembly I know has to change as well, but don't really have an information resource to ref for a complete guide.

I wasn't trying to discourage building a smallframe, they are super fun to ride. I just mean you can build a small frame to keep up with larger Vespa on longer rides and spend a lot of money or you can spend less money and have a small frame that is awesome for running around town (90% of the riding I do).

I didn't think you were Declan, I know you're just offering thoughts, which is exactly why I started this thread. I don't do a lot of long haul rides, I am mostly looking to just have something that reliably does ~50mph so I can cruise around me and maybe take the occasional trip to NYC for work, etc.

Still weighing 3/4 speed before I buy anything.

I rode a V90 around for a while, once for some distance with a small gang. I barely kept up by winding the piss out of it in second. Going up hills was the WORST, you got many hills to deal with? You could do it better with more than stockish V90 power, but the 4 speed is SO nice.

I have 90/100 primaries in both my mildly tuned 125 smallies and often just start in second - so that's like a 3 speed and it goes plenty fast. I run out of courage before I run out of gear in fourth with those primaries, but I also get a little 'upgear' running a 3.50 tire.

I'm definitely hilly by me here in Connecticut, especially if I wander northwest. That said, I'm not afraid of wringing out gears to get the revs I need.

My Lambretta Cento is 100cc/3spd and completely stock is a relaxed 45mph, but does need some love in 2nd to get hills at ~35mph.

I think I've muddled my way through a quick setup for 4-speed conversion, and while ~$300 isn't bad, it obviously could get used on other EQ.

I know Greasy stated the short 4th is ideal, but not sure if I'm ready to piece-out a gear set.

Always wanted a Cento, but there are so few of them and the parts situation - ugh. A starstream would be the Lammy smallframe to have but with the same caveats.

There is a short 3rd 3 speed tree
https://www.sip-scootershop.com/en/product/input-shaft-assembly-20-16-10-teeth-3-speed-drt_11202300

I built two motors with this clutch and will use it again. .5mm cover spacer and a thick gasket and minor material removal from the cover and brake backplate for clearance.
https://www.sip-scootershop.com/en/product/clutch-crimaz-cm4-cm4_40431910

The PM40 pipe and a 24mm carb make a world of difference over the SHB and peashooters

This fell into my lap as the forgotten project of a septuagenarian engineer whose real passion was restoring pre-war race cars (aka, a big dollars).

And parts aren't impossible with Rimini Lambretta Centre and Casa Performance putting out stuff, but price point entry is HIGH for performance on these. Which is why mine is stock for now. Although I need to do main seals this summer.

Also I have eccentric big end pins if your good with cranks.

I wish I was, but you until recently my garage was a single bay in Brooklyn with 16 bikes in it, so tooling was minimalist.

I hope to eventually get a small hydro press and build a truing setup.

Greasy and others already gave a lot of right info.

Just saying from myself.

Tried few smallies with 3 speed - really strange things, only one what I liked is off-road PK with 102cc Polini and 3.16 primary so you can ride on 3rd gear like on CVT-scoot and gains easily 60-65 km/h on dirt roads.

So 4 speed gear box is very good idea. Especially in combination with VMC short 4th tree. Or if it fits to your new 4th speed gear box - DRT Short 4th Gear Cog.

You can start with 27/69(2.56) primary eg. RMS or something more brandly. Then, if you don't like ratio what it gives, you can change only primary driven gear(without splitting cases) for longer with 28T Benelli, 28T DRT, 28T Polini or shorter with 26T Polini, 26T Benelli or even more shorter 25T DRT, 25T Benelli

If you want to stay with 19/20 crank this Mazzucchelli is the good one.
And in future you can use Crimaz adapter for new 20mm flywheel ignition
With DR or Polini cylinders you don't need a priced clutch. Just check if your old one is in good condition and put in new 3 or 4 plates kit(Newfren, Surflex, Malossi or Polini) with reinforced spring. Reinforced circlip also good part.

On my 50 Special with VMC 125cc and others stuff I used clutch what made from used cheap RMS(same as CIF or F.A.) basket, baseplate and outer friction plate, Malossi kit and reinf. SIP circlip with Crimaz pressure plate
All works perfect without any issues.
Yes with single spring clutch and reinf. spring you get hard clutch lever but much more less headache and less costs than fitting cool pricey clutch or XL2 clutch type.

With DR or Polini cylinders you really don't need that Egig pipe what you mentioned above.
Good old Polini Banana, new Polini Original, SIP Road Banana or VMC Tork is good pair.

24 or 25 carb is enough for your wants.