Modern Vespa

Do you have the original one with the metal oil tank?

It's probably the rubber rings that seal the banjo.

Be really careful with the banjo. They are made of soft aluminum, and impossible to find.

Mine broke when I was pulling out the tank.

I have one of those original tanks but opted for a new tank and plastic oil tank

I replaced mine, too. It was so rusty.

I think this is the way the hardware goes in there.

banjo, metal washer, rubber spacer, plastic tank, metal tank.

If you over fill the tank, the top part is more prone to leaking. but the bottom banjo-bolt thing has to be pretty tight.

Not the best fit but it will do for now (still have to deal with the cover but at least I can easily cart tools

So having jetting, air issues. So I am using a 130 main with a Be3 55/160 and it runs great with the air box top off but as soon as i put it on it bogs down and wont start after it dies.

My setup pinasco 215 with a brand new spaco 26/26e
any ideas? seems like its not getting enough air when the air box top is on.

Oh I am using a t5 airbox top to allow for more air.
Gonna try a 125 Mj and see if that helps

So heres what just happened. Put the 125 in got it idling and revving well, with the airbox on, ran it for like 5 mins, then shut it off to push it out of my garage and up a small hill. When i tried to start it again it took like 5 kicks and when it finally started it just bogged down and would only run half heartedly at full throttle which as soon as i release it it dies. Tis has happened also on almost every ride i have had. it runs well then i stop for a bit 10-20 mins and when i try to start it again it feels super weak and dies as soon as the throttle is released.
the only way i get it going again is to turn in the idle screw all the way.
itS baffling that it runs well, gets shut off and then is hard to start and runs like shit??

I was going to ask if it's possible something is blocking the air intake inside the chassis/under the seat. That's assuming you have the bellows hooked up when the air box cover is on. The previous owner of my Rally was in the habit of keeping a towel under the seat, and it eventually fell into the hole and cut off the air. Took him a few minutes to realize that's what happened.

I'm not great with carbs and jetting issues, but it almost sounds like you are flooding. Could your float be messed up? Maybe the air box is unrelated, and it's more an issue of time. Once you have the fuel tap on, you are slowly flooding out, so at first it starts up and runs OK, but as the flooding gets worse you have to open the throttle more and more (or put the idle screw all the way in) to compensate.

Along those same lines, what condition is the float needle? Brand new carb I bought came with a broken one, which made me pull my hair out for a while.

Yea that sounds possible. It's a brand new carb so I'm thinking (hoping) it's ok. But I will check everything now

Guess I know what I'm checking next!

Checked the needle and it looks great, float moves freely, no hang ups. I did lap the carb base a bit just in case but it seemed level. the airway under the seat is clear, bellows hooked up properly. I am thinking the fuel tap? I have an sip fast flow on there but I also have a new stock fuel tap I could swap out?
I agree with what Jack said it feels like its flooding out over time.....

You can easily troubleshoot all your float & float needle issues by sticking a paper towel under the fuel rod in the carb for a few minutes. If the towel had fuel on it, you have a leaky needle/seat/float. If it doesn't, you don't.

To check fuel flow, pull the fuel line off the carb and time how long it takes for a pint of fuel to flow out of the tank. If it's a minute or less, your fuel flow is fine.

Before you do any of that, though, get it into the failure mode, which is the motor a little bit warm, and put a timing light on it. I think you'll see that it's missing and/or misfiring.

I think you're chasing ghosts inside the carb and the real gremlins are going to turn out to be electrical. I get that you're wanting to keep it authentic, but see if you can borrow a Ducati ignition from someone and see if your problems go away.

If this is true and your float needle is good you might try burnishing your float needle seat, look over here: https://modernvespa.com/forum/post1823915#1823915

You lost me ... , please explain and help me out here. Do you mean just down the venturi? Simple and quick test! I like to do something similar when I can, but with carb & gas tank connected out of the bike because it tests the whole system for any leaks.

Yep, that's exactly what I mean. under the brass rod which injects the fuel into the venturi.

Whoa now everybody lost me!! I feel like an underclass man among phd's
And I'm hoping for an Occam's razor

I'm not concerned with authenticity, I actually have a pinasco cdi on it now. Just want it to run well

What Chandlerman is saying is, take the air box cover and air filter off; look down inside the carb venturi where the throttle slide is, and you will see the little brass tube that feeds fuel in. Put a paper towel down there with the fuel tap on, don't touch the throttle, and see if fuel is still coming into the carb. If so, something is up with your float setup. If not, the problem is elsewhere.

His next point on electrical issues is probably where I would go next as well. When the stator wiring in my Rally rotted, it would start OK but as soon as you added power it would bog and misfire and run like crap. I somehow limped it home eventually and eventually got help diagnosing it thanks to someone on this forum. You've had it all apart so I'm sure you would know if your wiring is bad, but if the CDI is failing it could produce the same symptoms. A timing light will show you if you are getting a steady spark or if it's all over the place. I don't actually have one, I should add it to my list...

Thanks for breaking that down. I have a lambretta friend with a timing light so that's gonna happen but first I will do the paper towel.

Cool. I think it's going to come out dry in the morning.

When it comes to troubleshooting, I'm all about fault isolation.

I've had ignitions (usually CDI's) fail on me a few times, and your issues sound like a lot more like that than a carb that only decides to misbehave after it's warmed up a little.

I quit running Pinasco Flytech's once the SIP/Vape came out because I was sick of the CDI's failing in a similar manner to what you're describing.

Yup indeed. Left the towel in overnight and this morning it was dry. My friends gonna help with the timing light on sunday

Welp learn the hard way! A while back I posted about my oil tank leaking. Finally got around to it and damn what a messy fix! Oil everywhere! I forgot this hose clip and that's where it was coming from. Managed to sop up a lot of the oil in the channel but I'm sure there is more. Anyway that was messy but fun

Well, at least it's rust protected even more with the oil now!

A small win but i'll take it! So did the timing light with my friend today and we checked TDC and it was right on, put a timing light on it and it was steady, strong and at the correct point. He thought it may be a carb box issue because when we looked inside the T5 airbox lid it did have some scrapes in the rear left corner right where the float chamber top is. He said if that rubs on the box most likely its affecting the float and the reason Im flooding out once warm. We modified it a bit (aka banged it out with a hammer) and I took it for a spin.
It did great until it hit 216 degrees or so then it stalled at a stop sign and died. After that it wouldn't kick over again and I had to walk it home (kind of pushed it with my left leg while sitting like skateboard).
So he sent me this FMP Video on SI 24 warm start flooded engine and I think its spot on.....found the next rabbit hole , wheee

Questions:
Do you have another carb to try?
Why a T5 carb?

Some things:
Take it out to stall again and pull the plug. Looks wet?
See if it sparks grounded against the case while hot.

Should provide more clues. You'd also need to open the slide and stick the paper towel inside for that needle test. It'll leak below the slide before the tube.
Good luck!

It's just a t5 air box lid. I heard they are good for kitted engines because they are taller and have more air

as an FYI, the later model PX and Stella scooters came with the tall T5 style carb box cover.

Well after many frustrating rabbit holes gone down I realized I had an air leak (or two!) One on the cylinder base and the other on the fly side seal. Thanks MJRally for the patient help. Got everything sorted and took her on a test ride and now every thing seems better, or at least like I am going down the correct rabbit hole! I unfortunately got sick this weekend so couldn't take it on a long ride to really put it through its paces, but on a short ride I got to the temp where failure usually occurred and it did not fail! Jetting seemed great and responsive. Soon I will take her on a proper test ride but wanted to check in!
So it seems all the symptoms I thought were carb or electrical issues were actually air leaks, at least thats what I am deducing....

So I may have fucked up. I got a sip vape ignition the ac kind cause I don't have a battery. I thought the pinasco ignition may have been the root of my problems. When I took it apart I found that the wires were so loose on there that may have well been the problem. But I got the sip ignition and am excited about it so I proceeded. The first photo is how the guy I hired to hook it up had it set up. The green blue double yellow and orange from the harness were hooked up to a red from the stator. And that screw was so loose! The second pic is the new wires and when I look at the sip vid it seems so easy but then I look at my situation and feel overwhelmed. Any help would be so appreciated.

White and red go in a plastic piece that came with the Vape, then attached to the red and white coming off the CDI.

Brown gets grounded to the Vape bracket that attaches to the engine case.

Blue/white is the kill wire attachment as well so your kill wire attaches to that.

Blue and black from the stator go to the junction. Not sure where you go after though.

Blue from the stator goes to the regulator (either yellow).

Black from the stator goes to ground.

AC to the harness goes to the *other* yellow on the regulator.

I have a similar pile of ring terminals on most of my bikes because what were originally separate circuits are all bundled together with a modern ignition. If it makes you feel dirty to know that's in your junction box, you could crimp together a bridge and spread the circuits out that way.

Also, I run DC without a battery in my VBB. I just omitted the battery and all is well. If you want to go that route, it's a straight swap of the Vape regulator to a regulator/rectifier, which you can buy just the rectifier and it won't break the bank.

Thanks guys I am going to wrench tomorrow or monday with handholding from an MV member. I will let you know how it goes! Oh and CM i like that idea of the dc rectifier, next time I hace to place an sip order that may be the ticket!

Had a great wrenching session with MJ Rally on pier 17 in sf! Thanks for the electrical help.

Took a break from work and had some fun pierside. Wasn't too difficult deciphering the spaghetti wiring. All went well till Cdevillesante dropped a live extension cord in the water Glad it's still working!

shhhhhhhhh

Sooo took double yellow out n about today about a 36 mile round trip to a few towns over. She did awesome but I noticed the temp gauge was getting up to about 289 ish max. Is that high? Or normal. Felt and sounded fine. I didn't get a pic but will next time. The bugs though on these country roads at night! The legshield looks like a battlefield oh the carnage ! (The pic below is from a couple rides ago)

Can you tell me name and color code of this yellow?

Hey here is the code. I think my painter just eyeballed it haha