Re: Epic Vespa Thread


I drilled a second hole in the float bowl and I was almost ready to go. I needed to figure out a way to seal up the hole around the brass tube while still being able to disassemble the carb.


Goo did not work.


This suggestion came from a Moped Army member, but I forget who. The tubing was pushed up into the hole first, then the brass tube was forced through.

Better, but still leaky.

Re: Epic Vespa Thread


I tried another kind of fuel tube. Unfortunately, this leaked too. I eventually went back to the hobby shop and got some black neoprene fuel tube, and that stuff worked well.


In the mean time, I had been testing the needle valve. While the leaks were happening, the needle valve was also working! I was able to reliably control the mixture that fed the engine.

One thing I had a hard time with though was throttle response. This first setup with the needle valve out of the subframe had long tubes, which killed throttle response. Fuel delivery in these small carbs is accomplished by gravity feed and suction from the venturi. I figured out that if I shortened the fuel loop, I could fix it.


When I fixed the leak, I also shortened the tubes and cleaned up the design. The wire sticking out from the valve allows me to turn it without reaching under the engine. If I ride slow, I can change my mixture while rolling.

As you saw in one of my earlier posts, I ended up trading for a different needle valve later on. It was just a nicer valve. I put a lot of miles on this particular valve and had no troubles.

I did have a couple of soft seizes when I was learning about tuning, but that was my fault, not caused by the needle valve. Same thing could have happened with jets.

Re: Epic Vespa Thread

Was there any benefit to it once it was set vs swapping out the main jet? Did it help with rich low mid throttle?

Re: Epic Vespa Thread

hmm, to make it easier, couldn't u just go from tank to needle valve to brass tubing /jet and ditching the whole float/ float bowl, or am i missing something.

Re: Epic Vespa Thread

@ joe

There hasn't been a huge payoff, no. Other than, I can swap pipes anytime I want and not have to change jets. But that doesn't happen much, I know. The biggest payoff for me was just being able to make it happen.

However, now I've kitted that bike and I'll have a temp gauge to help me tune. We'll see how much I can get out of it.

This won't affect the low mid high issue because that is tuned by the emulsion tube, not the jet. I've also read you can play with the slide to affect that.


Without the float system you have no way of metering the fuel flow. The purpose of the float system is to keep the bowl from overflowing when the engine is at idle. If you bypassed the float and went directly to the needle valve, you'd be flooding your engine all the time. The needle valve doesn't open and close, it is simply a pinch point to control how much fuel can flow through it at once. If you bypassed the float system with a regular jet, you'd have the same issue.

Re: Epic Vespa Thread

^^thats right, i knew i was missing something. Was just imagining a .049 with that tiny carb and a hose attached to it w no float bowl.

but the tank is level and you have to prime it. on the larger engines theres also that pressure line off the exhaust to the tank as well.

Re: Epic Vespa Thread

To tease you, here is a picture of my newly completed Proma modification! The pipe has been turned to the side to make it more like a dirt bike.


The back story: these amazing wheels deserved to be on a bike. They're Grande wheels and I didn't have a Grande to put them on, so I put them on this Bravo. I swapped forks for Grande forks as well. I added longer shocks to the rear and now the bike has more height as well as being beefier. I added the longer shocks because I had rear fender clearance issues. Well, that caused the front fender to rub against the pipe. Saw an awesome modded pipe on a Bravo dirtped on the treats Instagram feed and decided to give it a try. Soon I'll post all the process pics.

Re: Epic Vespa Thread

So we all know what a Proma looks like under a Vespa. To change it up to a side pipe was not all that difficult, especially with help from Ed's Moped Shop.


Step 1 was to make this cut. The spot was chosen strategically to use the existing bend to angle the pipe out and away from the tank.


A little trial and error and test fitting happened. You'll notice the singer and baffle were also cut off. This was to allow an adjustment for the bend of the stinger again.


The stinger was reattached with the bracket left in place. It would be used to support the pipe as before, albeit in a different place.

Re: Epic Vespa Thread


A tab was added to the pipe with the intent of using the bottom engine bolt as a support. For that purpose, the bottom bolt was replaced with an m6 threaded rod.


After trimming the rod, you can see how I used nuts to connect to the threaded rod. Nuts in both sides to lock it in place. It'll be a bit trickier to remove the pipe, but well worth the effort.

The rear mount was done much the same way. I had leftover rod to make it with. A hole was drilled in the subframe for this purpose. It was drilled as close to the upper lip as possible to avoid interference with the belt.


The primer and paint I used are both for engine blocks, so it should hold up OK. I put one coat of primer and 4 or 5 coats of black.

Re: Epic Vespa Thread

Is that a GY6 variator?

Re: Epic Vespa Thread

Dirty30 Dillon /

I would have welded a nut to the front pipe mount and used that as the but for the stock engine bolt. Threaded rod is not the most confidence inspiring hardware, doubly so given that these tend to break subframes anyways (especially when taken off-road).

Re: Epic Vespa Thread

I played Vespa exhaust this week as well. I took Jake Cain’s Doppler pipe specs to build this one. I’ve been wanting to try the side bleed so I welded the stinger pipe into the belly.


Re: Epic Vespa Thread

it's cool to see some of the dumb ideas I threw at ciaociao stuck, the ktm ignition really makes a vespa rip. you can do a fan, I did on the original ktm ignition Vespa, but the plastic tfr fans are hard to find these days.

I'm trying to get ciaociao back from my buddy, we had a "I'll sell it to you if you promise to sell it back for the same price someday" deal, but I'm pretty broke these days

I never did the scooter clutch mod, mostly cos kids were still trying to figure it out back when I built ciaociao, but also because the stock 3 tier Vespa clutch bell was working just fine for me. I've only ever seen Vespa bells explode when revved out on the stand and my ciao never had a stand, so it was fine by me. Also, I wasn't sure if there's really any performance benefits, my ciao was gpsd at 63 and wanted to wheelie everywhere with the Vespa clutch, which was scary enough. Tho it did shred belts, I had to put on a new belt every other rally.

I miss ciaociao


Re: Epic Vespa Thread

I’m excited to see how the ktm rotor reacts, do you by chance remember what you set your timing to on ciao ciao?

Re: Epic Vespa Thread

Dirty30 Dillon /

CiaoCiao is the reason I own 3 ciaos

Re: Epic Vespa Thread

> - Joe - Wrote:

> -------------------------------------------------------

> I’m excited to see how the ktm rotor reacts, do you by chance remember

> what you set your timing to on ciao ciao?

I don't remember, it may be in the blog tho

Re: Epic Vespa Thread

> discontinuuity _ Wrote:

> -------------------------------------------------------

> Is that a GY6 variator?

That's a Graham Motzing special.


That pipe looks spectacular!

Re: Epic Vespa Thread

I treated the grande to a ebc rear brake pad. You can see how much wider the after market pads/kinetic pads are vs stock.


Re: Epic Vespa Thread

kinetic are even wider still!


Re: Epic Vespa Thread

Damn, I have kinetic pads in 2 of my other bikes I didn’t realize they were that much wider.

Re: Epic Vespa Thread

Wow! Are there new Kinetic pads or just old ones? Those things are awesome!


Got this out today. GPSed at 37, but I think it has more to give. I will be trying some more fine tuning.


Got some shorty pedal cranks for it.


Pedals now clear beautifully!

Re: Epic Vespa Thread



My good friend has made these! I'm doing a bit of finishing on them. I will be staining and adding poly.


Re: Epic Vespa Thread

> Ike Pipe Wrote:

> -------------------------------------------------------

> Jo


> My good friend has made these! I'm doing a bit of finishing on them. I

> will be staining and adding poly.

> >

Maybe rout the edges ?

Lookin' pretty good , even so .

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