Modern Vespa

Good day everyone, I just finally after 5 years got my 100 Sport running. It does have a DR kit on it and SIP banana pipe. The issue I am having is going into 3rd gear. The scoot has plenty of power in 1st and 2nd but it bogs down in 3rd but then catches back up. I am thinking it is a jetting issue but wanted your input before I pull the carb and change the jet. Thanks in advance.

it's more than likely the giant gap between 2nd & 3rd gear. unless you leg it wayyy out when you make the jump you wind up down low in the RPM so you're square out of the powerband and then need to slowly catch back up.

I had some similar problems on my smallframe (sport 100, 19carb, kidney pipe).

I'd check for air leaks if you can- I had a tiny air leak on the intake manifold that only presented itself as a problem at a higher RPM range. The other thing I found was that the jetting was very impacted by the air filter. It would run great with no air filter and then bog badly with the stock airfilter on. My solution was modifying a cheap metal mesh airflter to fit.

THIS pretty much says it. In my experience, that 2-3 gear gap is a bummer, and almost impossible to stay in powerband when shifting to 3rd gear. Especially on a bone stocker build. Obiviously mosdef check for any air leaks, and your jetting; but unfortunatley that 3speed gearing is just not great to begin with.

Thanks everyone, I do think it is the gear gap as it eventually gets up and moves. In 1st and 2nd its screams. Thank you again.

is a 100 sport 3 speed in stock form?

Yes sir, to the best of my knowledge. I have read where some have converted to 4 speed.

Yes, the 100 Sport is factory 3 speed. The 2 - 3 gap is pretty huge. Easily changed to 4 speed, using later Primavera/125/PK gears. Just need the 4 x gears, 4 speed cruciform, and 4 speed 'xmas tree'. The original drive shaft can be reused.


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And a tiny bit of Tipp-Ex to mark a '4' on your gear shifter under the '3' £1.75 amazon This is of course tongue in cheek. Talking about Tipp-Ex, I knew somebody who once mistakenly swallowed this instead of his Viagra. He had a huge correction all night.

It is!
Is that all you did on your otherwise-stock 100 Sport?

As far as the gearing goes, yes that is all that I did. For an extra little punch DRT makes a 'short-4th' gear tree that reduces the 3-4 gap, and makes getting into 4th even smoother than stock. Its not so much needed on a stock build, but shows its strength in a tuned/touring build when hitting the hills.

I have recently moved along my 100 Sport, and it was not stock. It had the 4 gear swap, short 4th tree, uprated clutch, race cut crank, Polini 130 kit ported and matched, machined head, 24m PWK carb, Jim Lomas Pipe, 12v Ducati ignition, and light flywheel. Fun little scoot!!

I bought that DOD 100 Sport. Seller turned out to be a friend of a friend.
He was getting ready to ship it to Portugal.

Learning a lot digging in the crates in the older threads here, and of course came across yours.
My one question is will a banana exhaust fit with a battery. Haven't found an old answer to that yet.

Meanwhile I'm loving the idea of digging into this upside-down, sideways engine.

Everything works except the neutral light and the horn. First kick bike that would otherwise be much more fun if I didn't have to get home up a crazy-steep hill climb. Getting caught under that power band is wild.

Original tail light and engine door came in a box along with, but the turn signals are long gone.
Thinking bar end turn signals and hopefully a battery.

The rest pretty much your build, save for the pipe and carb.

Can't say. The Malossi banana on my ET3 has never had an issue with the built in storage compartment, even while riding 2 up. I think the storage is larger than a battery box.

This:

https://www.scootermercato.com/Scooter-Parts/Polini/200-2025-S

It will work with the us battery box. The et3 box is smaller and less constrictive. But the polini is a great exhaust that fits, no cutting.

it's not so much the size of the battery box but the trailing edge that hangs up on pipes.

the short answer is maybe it'll fit.

the longer answer is be sure that the motor and shock mounts are in perfect condition and you've got the right shock to start with.

I know that the kidney style pipes fit, although sometimes rub on the body up higher so that's an option. I think birbs is running the sip banana on his American market primmy which is the same batt box.

I've got the Carbone Sport and Sip banana on my big long list, so far.
Solved the Polini box on 8's with that one (adjustable preload) and a spacer, so hoping for the best.

Gotta be two-up up worthy or I'll get strangled in my sleep by my wife, once she sees the bill