Modern Vespa

Hi from Paris, France. This is my first post on the forum !
I decided to create a post after being a long time reader. This forum helped my a lot to fix my Vespa GTS 300 Supersport 2010... So thank you all.

For now, I really need someone's wise help!

(I used to read the GTS300 Workshop manual which is really helpful but not for my case. So i just bought the Haynes manual which is very complete)

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Here is my problem :

I recently decided to change my cylinder head, cylinder and piston of my scooter after 37 000km of good ride.
I changed my injector too because of a faulty old one. Bought a used old injector (white ring, the new injectors have orange ring). I think it's crappy.
Just to know it, for now i realised that i missed a collector outlet gasket in my engine rebuilding.

After running the engine, it misfires, doesn't run smoothly, there is a lot white-blue smoke (fuel smell) and it stalls.

My compression ratio is around 8bar (110 psi).
I decided to put some oil in the spark plug hole to know if the cylinder was the problem. Compression ratio got up to 10bar (150 psi).
So there is no doubt (can someone confirm ?), my piston rings are involved at least in the engine misfire. That test is excluding the valve sealing gaskets for sure ?

My question is, what is the piston ring's gap exact position ??
I've disassembled my engine 3 times to replace those rings (the cylinder and the piston weren't worn fortunately!!) ! There is not even a real information about it on the internet...

In the Haynes manual they say .. (look at the white image attached)
But in Robot's from ScooterWest video on YT (https://www.youtube.com/watch?v=NxN0AIYWrVc&t=838s) I'm not sure but i think i understood this .. (look at the grey image attached)

Which one is right ? Is that setting really valuable for a smooth run ?

For my white-blue smoke, i've checked the sparkplug and it's black, but not oily. I think of a too rich ratio due to my crappy used injector which injects too much fuel compared to the old one (the old one has a misconnection).

Can someone confirm it ?

For the stalling... I don't know. Maybe a combination of those two problems ?

In JPDIAG, i have a P0335 error code : seems to be the camshaft sensor into the stator according to some posts i've read on this forum. Can someone confirm?
My stator is really really dirty full of oil, can this have an impact on something above?


Here is 2 videos of the symptoms :
https://www.youtube.com/watch?v=iF3peo1zrLY
https://www.youtube.com/watch?v=IgSu2pHm-X4

Thank a lot for reading me ! Sorry for the long post...

Thibaut

All the time and money you've spent on this thing, and you put in the wrong injector. Fix that first.

The ring intervals is not important, as long as they are not all lined up. That's not your problem, unless you trimmed the ends. If you have altered the rings in any way, get new ones.

Put whatever you left out back in and make sure you verify the cam timing at the crank.

Going by the sound alone the camshaft and/or ignition timing could be out. The error code does suggest that correct ignition and injection timing could be impossible due to crank position sensor problems, could that be connected? Perhaps the rotor is loose?

As Motovista says...you must replace the injector with the correct one. That's the first thing to do. Then you can start to sort through other issues if that does not have the desired effect. A faulty or incorrect injector will cause all the issues you are complaining of. I've had bikes come into the workshop sounding just like yours, smoking too, and all it took to fix it was a new injector. There may well be other issues with your motor, but sort the injector first. Work methodically through the engine. Keep us all informed so we can try to help you with this. Good luck!

Guys ! Thank you so much for your wise advises !

It works with a brand new injector !!

I was a little bit confused at the beginning because of the white smoke persisting... but after a 5 min ride in ny neighbourhood, it came off !!!

This is my first big work on this engine, and i'm very happy of this ending !! My Scooter has a new top-end engine life!!!

Now i'm going to buy a new (but used) muffler for 100EUR and i'll keep on riding in Paris's cold nights !!

And maybe in a near future, a whole black brilliant paint, to give it a new -looking- life!

I'll keep an eye on the rotor, because it is very dirty inside.

Thank you all for your help !

(That was so easy and dumb haha)

Thibaut (that's me)

b0risblade, you are certainly not dumb! Well done for fixing the issue and reporting back on how it went. Thank you. It helps everyone.