Modern Vespa

Evening all, I'm pulling my hair out here.
Any help would be very gratefully received.

My PX 125 2015 elec start was struggling to start. I couldn't get a spark. I changed the static plate and the CDI now I get a spark. I also have fuel to the carb.
I cannot get her to start. I do get a pop every few turns and exhaust fumes coming out of the air filter. What I don't get is any indication she wants to start.
Plug gap checked.

Please help me. Any ideas what could be ailing the old girl.

Many many thanks in advance.

Cheers Mikey

simple stuff first - have you tried a new plug? could be fouled.

Have you checked compression? That's what I'd be looking at..

Did you put the new stator plate in the exact same spot the old one was at? If miss-timed, she'll backfire on you.

Thanks for the quick response fellas

It is a newish plug, and it is sparking well

Compression, I'm not sure how to check but when I kick it over with the carb cover off it feels like it has compression. If there is another way to check compression let me know please and I'll give it a shot.

I'm sure I put the stator plate back exactly the same as the old one but I'm second guessing myself now! I'll go and check. Thanks again, I'll let you know how I get on

on the plug - use a new one anyway, they can foul and still spark outside the engine

on the compression - you need a guage

on the stator - line up at IT mark and it should be good enough to start

I've took the flywheel off again to check position of stator plate. It is the same as the old one. Set to IT and not A

I do have a couple of new plugs coming tomorrow so will swap those over just in case

What ignition is that? (I'm not concerned, just curious)

Sorry but I'm not sure what you mean by what ignition? It's a 2015 PX125
It's got electric start in addition to the usual kick start if that makes sense?

Did you reinstall the woodruff key? The slot for it is at the 6 o'clock position in this pic. Should be installed and matched to the same groove on the flywheel. Then flywheel needs to be torqued to 45 ft/lbs

that's not a standard looking PX stator plate is what the c-man is saying.

they look like this:

Later model Euro 2-3???? had different stators.

Woodruff key?
No i didn't, didn't know I had one!
I've just found this bigger on the floor, I didn't have a clue what it was!

This. I assumed you had replaced it with an aftermarket and was curious which one it was.

With that out of the way, assuming you have spark, and given you have an aftermarket starter of unknown provenance, it might be a good idea to check your timing.

Do a search for how to find TDC and set ignition timing. If you just want to know if it's in the ballpark, you can remove your plug and eyeball TDC. That, like the marks on the stator, will get you close enough that you'll know if it's firing at a point it could theoretically run.

Made in China?

That's very strange.
This is a picture of the log book

The stator plate says made in China on it

interesting - do they look like what he's got? or is his something else altogether?

Late Euro PX Chinese made Kokusan ignition with over revving retard. All parts are unique to this and not compatible to Ducati type ignition…

Yep! Chinese overlords are even taking our stators now

Mikey- install the woodruff key in the slot on the crankshaft, torque down the flywheel again and she should start.

Got it CMan
Installed Woodruff Key and it starts on first kick. They say everyday is a school day. I've learned a lot today. Not least how generous you guys are with your advice.
Thanks to you all

and after all that, it looks like we've solved it. The woodruff key indexes the flywheel to the crank to ensure the spark triggers at the right time.

When you reinstall the flywheel with the woodruff key in place, you'll have to get it properly aligned or the flywheel won't want to seat onto the crank right. Don't try to force it if it doesn't slip all the way on. Lift the flywheel off and try again until you get it.

I really shouldn't be surprised that Vespa went to China for stators in the early 2000's (I spent enough time in Chinese factories in those days to know better), but I still kind've am.

To be fair, I've had her for over 9 years now without a problem. This one flummoxed me but I'm so grateful that you helped to solve it. I noticed the key on the garage floor and picked it us Turned it over and couldn't figure out what it was or where it had came from. I put it in a safe place 'just in case'
Good job I did!
Thanks again for your help👍👍

Evening guys.
Everything going well with my PX 125.
It runs better than ever at high recs. However. When at low revs it's a different story. When I give the throttle a little tweak, the first thing she does is slow down, just briefly but almost to the point of stalling.
It does this even when warm.
When she's running at speed and higher revs she runs so well.
Remembering this is a Chinese build. Do any of you guys have an inkling what could be the problem.
As always, many thanks in advance
Cheers
Mick

Your idle mixture is off. It could be as simple as adjusting the Mixture screw on the back of the carb (through the hole in the airbox) or cleaning the idle jet.

Can you share a video so we can hear what it's doing? The symptom you're describing can be both rich and lean at the level of detail you're giving us.

I can't load a video to the forum for some reason I keep getting an error message but I have uploaded it to youtube. If you copy and paste the link below
This is after it has warmed up.
You will see it takes a while to return to normal tickover and also hopefully see the down tick before the revs pick up when a little throttle is applied

Another thing that may be important. It's still very reluctant to start. It will take 20-25 kicks then after turning off the fuel tap will eventually start. So it can be done but it does take an age.

Got set the video's visibility to "Unlisted," not "Private" if you want us to see it.

Apologies, changed to unlisted

Pilot jet blocked? In the end tip of the pilot jet is a tiny hole. Probably blocked. Need to poke it with a stiff fine wire.

Agreed.

Get the idle jet clean and try it again.

Thanks Jack and C Man
I checked this morningg and the idle jet was blocked, I cleaned it with carb vleaner and took her outr for a good long run this morning. The throttle proiblem has definitely been fixed Thank you so much. It's very responsive.

The one last minor thing That you also may have a simple answer to....
When I'm twatting along at 50mph It runs beautifully and then every now and again will 'miss' I don't know how else to describe, it just seem to miss a beat I can hear it and feel it, then runs perfectly again then miss another beat.

I can live with this as she is running again which is a massive bonus but if it's a quick fix...

I don't know if it's connected but I have never really been happy with the mixture, I've got her running but I can't find anywhere what the number of turns the mixture screw should be at. I've turned it 2 full turns as that seems to be the consensus but as you've pointed out, my carb is a bit different from the standard for some reason

My initial guess is that it's slipping out of resonance due to being a hair too rich.

What throttle position are you at and what gear are you in when it misses?

Without knowing the throttle position pretty precisely, I can't suggest a change.

If it's Wide-Open Throttle (WOT), you might need to drop your main jet one size, but I'd like to hear at least audio (start the recorder and stick it in your back pocket) before I suggest that.

Hi Cman,
Thanks for your response. It's when the revs are quite high but not just WOT
I also suspect it's a little bit rich so I would like to experiment with weakening the mixture slightly.
If I just make 1/8th turn adjustments I should be able to weed this problem out.
Next question, to weaken the mixture do I go in clockwise or out anti clockwise?

If that doesn't work I can work on getting a recording for you

By "weaken," I assume you mean lean it out. The screw controls the low speed fuel flow, so you turn it in (clockwise) to lean it.

The low speed circuit contributes across the entire rev range, but obviously the contribution becomes a smaller and smaller component.

I still think you're going to need to go down a jet if it's so rich it's stumbling. That's a good place to be, though. If you're going to start playing with jetting, I'd suggest getting a set of jets from a reputable source. The measures can vary depending on the source (e.g. a Dellorto main is ten points richer than a SIP main of the same "size"), but they'll at least be consistent with each other.

Thanks Cman, standby

Are you still running with the catalytic converter exhaust?
These modern motors run lean for the emissions. Might be that.

How can I tell if it's a catalytic converter exhaust? is there an easy way to find out? it's a 2015 model

Easiest is if you know if it's the factory exhaust or not.

On the LML Star/Stella, it had a little heat shield over the catalytic converter between the manifold and the box.