Modern Vespa

Hey everyone, I’m hoping someone can help. I’ve scoured previous posts and videos but my current problem is quite tricky to search for...

I bought an ET2 that was having trouble starting, it turns over but no fire. I’ve been working through all the recommended steps, I’ll list what I’ve done so far at the bottom. but the only time it has actually got running was when the fuel was not hooked up. I was testing whether the vacuum was working so had the fuel hose off and going into a bucket, the scooter started(!) Then without fuel it started again and again perfectly. I thought maybe the engine was flooded so I rode it down my drive until it burned off whatever fuel was in there (maybe this was big mistake?) and then reconnected everything. The engine hasn’t started since. I’m flummoxed. It seems logical that the fuel is the issue but I’m not wise enough to know what my next steps are.

Oh yes and now when I try and start it sounds much more pathetic than it has done previously like it’s battery is low but I still get a 11.46 on the multimeter at the batt and have one of those external charging things telling me the batt is fully charged. perhaps I need to check the charge is actually reaching the starter? Or somewhere else?

So far I have -

Drained and replaced the fuel
Changed the fuel tap
Tested the vacuum line
Changed the spark plug
Tested the spark
Charged and checked the battery and fuse
Checked the automatic choke
Changed the air filter
Cleaned the carburettor

I think that’s it, there’s probably some key info I’ve missed out.

Hope that makes some form of sense and sorry if I’ve misnamed things.. I am quite good at following internet instructions but this is my first scooter so I am a novice

Thanks so much

Annie

Hey the Petcock is vacuum operated, and also has a screen fuel filter attached inside tank, there is a vacuum pipe and fuel pipe, the vacuum pipe goes to intake manifold, to test suck on vacuum pipe and fuel should flow out of fuel line, these Petcock often fail, are the pipes
correctly assembled, is the screen filter clean.

On side of carb near top is a short black pipe, that doesn't go any where, this is a pressure vacuum relief and.fits on a inlet tube that goes to top of float bowl via internal passage, if this is blocked the engine will not be able to suck fuel through carb, and so maybe when you took off fuel line the vacuum was relieved allowing engine to suck fuel.

11.46 volts is low, should be 12:5 to 13,5 volts. Only small batteries they get too low quickly to turn engine fast enough. You got a motorbike charger or Car charger, cause car chargers will not charge them.

Hey, change out vacuum and fuel line for new,connect pipes and then disconnect fuel line from carb and then turn over engine, do you have fuel running out, I like to fit see through fuel hose so I can see fuel filling hose to carb, a garden machinery shop or good garden centre will stock it or order off ebay,
Attach jump leads too Battey from car or another bike and try too raise voltage, some modern chargers will not charge if voltage too low, see if you can raise voltage to 12volt and then try charging.

Hi Annie... welcome to the forum!

Given it ran (although briefly), I'd be inclined to think it's a relatively minor problem. It sound related to fuel delivery, as you say.

When you were testing the fuel line, did it work as expected? In other words, no fuel came out that line initially. Then it started to flow as you cranked / started the bike?

When you had the carb apart for cleaning, did you check on the float bowl? I'm wondering if there's something going on in the carb that might be leading to flooding: maybe float is cracked / not floating? Maybe the float height is set wrong? Maybe the float needle is not seating and fuel keeps pouring even when float bowl is full?

I have an et2, if you are interested in mods that simplify the machine a bit.

Take your oil pump out.
Get a vintage style premix cup
Switch out the vacuum petcock for a manual one:
https://scooterpartsco.com/ricambi/021-vespa/manual-fuel-valve-for-vespa-piaggio
Then plug vacuum line and oil inlet.
No need for the 2 stroke oil tank now.
Just measure out 2t oil at the pump per gallon or .25 gallon at 40:1 mix
Close manual tap when not in use.

This is basically my set-up

I don’t think I would go down that road when it sounds like she’s close to getting this thing going. There are some good suggestions upthread I’d certainly try first. I am intrigued with this. Where is the manual petcock? Is it easy to get to?

All the bikes I had in my youth had 3 way manual petcocks - off, on, reserve. Changing the petcock position was just part of start up and shut down. I guess Piaggio went with the vacuum petcock to make these things more appliance-like. But I’ve read enough posts about the vacuum petcocks failing that a manual petcock seems a decent idea.

good morning thanks for all your replies and warm welcomes!... now saturday has finally rolled round I have some time to work on it!

In regards to the vacuum and fuel line - I have changed the tap and filter and changed the both the fuel and vacuum lines. It was actually when I was testing whether fuel was flowing that the scooter turned on, the fuel did flow when the scooter was on and when I crank it. Its a good idea to have transparent pipes though I will try pick some up today.
I also have the carb out and am able to blow down the relief line but I will give a thorough clean later just to be safe. Ah I have a car charger actually, would it be better to try jumping it off the car? I think its probably worth investing in a new battery Yes the fuel flowed only when I was either cranking or running the bike.

I have suspicions about the float bowl, I have got it all apart currently. I can't see any cracks or impairments but when I have been researching the carb (dellorto phva 17.5) and in my haynes there are three adjustable jets (power, idle and main).. mine doesnt appear to have an adjustable power jet rather just an inlet (see ggl drive link) is this normal?

I'll see if i can test all the other things you have suggested with the float, maybe i'll get it up and running today!

Thanks so much for all the help everyone

Annie

PS thanks for the tips! i will definitely being continuing to tinker once i've got it going so I'll be sure to check this out.

https://drive.google.com/file/d/1HoIy6OIqq_he1gam1p18aKjJWVXJXELE/view?usp=sharing

hey, is is 2t or 4t, two stroke or four stroke, i run 4t et4125 that i rebuilt from a non runner basket case, so not got same carb, but will try my best to help,
to test if float chamber is working correctly, blow through fuel inlet pipe with carb upright, float should hang down, should let in air, turn carb upside down and blow again, the float should be level and valve closed, so no air should flow,
the float must be level when upside down, there is a metal tab on float with a float valve attached by a bit of wire, this fits in a hole or valve seat, you can bend the metal tab up or down a tiny bit to make float level,
if the float does not seal and stop you blowing through whilst carb upside, u will need to knock out pin that hinges plastic float, make sure you have the correct size tool, thin enough to do this, or you will damage float , carefully knock out pin, dont break alloy casting, try and support alloy pillar as you knock out pin, then clean out valve seat with carb cleaner an q tip, examine float valve for wear damage dirt, shake float if it has liquid inside its no good.
float valve can also stick shut and not let air through
ultimately new carb is easy option, and realitively cheap for your scooter

i have often found that when im sure its a carb issue its not, and i waste a shed load of money and time,
it could also be an electical issue, iid check plug cap is on properly, and is wound on tight to cable, and clean electric connections on coil , do indicators work ok?

there are a main jet and idle jet and a jet or tube for the choke or cold start circuit, these are brass and can be found in float bowl chamber, if you take off bottom off float bowl on bottom of carb and turn carb upside down, normally only the main jet and idle jet can be removed, with the correct fitting flat head screw driver, be carefull not to damage soft brass screw head. when you get them out hold up to light and check all little holes are open, you can use multi strand electrical copper wire to unblock and clean little holes, with the appropriate number of little strands of copper, and shoot through carb cleaner,
the idle jet provides small ammount of fuel, to scoot running until you open throttle and pull fuel through main jet. there will be a third brass tube that provides fuel for cold start until auto choke heats up and extends a pin shutting circuit off.
there are is also an idle mix screw on outside of carb that lets you set amount of air fuel at idle, 2.5 turn from closed fully clockwise in, and maybe an idle speed adjuster on air butterfly, where throttle cable is attached to carb.

I am not familiar with this carb. But given the bike ran (without fuel line attached), I am not sure the problem would be jetting?