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Pls see pic, there is a plethora of diaphragmas out
at APRILIA, VESPA, YAMAHA etc. dealers.
They just don't want to search in their storages...

Thanks for this precious hint. With this I am pretty sure to find something that fits. At least for the brakefluid reservoirs.

And yes, I have already contacted Meister ZIP in Germany. No success.

@Like 50
No. 1) The original Kenda Tires are Nylon Tires which are ok on clean, dry paved roads. They need to be ridden very carefully in rainy conditions and with only small bank angles. And a total no go in snowy road conditions.
No. 2) I am not aware of one single scooter or motorcycle tire (regardless of the size/diameter) that could handle well a 45 degree bank angle over tramway steels.   So, better take it easy over the rails in a more upright position.

I live in a City with lots of tramway rails, where I regularily cross these, sometimes even in pretty acute angles but always in a nearly upright position with litte bank angles. Never fell and crashed for dekades there. 

No 3) Make sure you are riding with proper tire pressure. 1,75 front, 2,0 - 2,3 rear (bar).

Stay and ride safe!

This is another interesting 5 page long mysterious unsolved story of a defect scooter - which is usually rocksolid and reliable, if treated nicely. Although so many forum members tried to help and put so much effort into it, the owners just opted out all of a sudden. Hmmmm....

After reading carefully what Renee wrote and watching the videos of the cylinder head and the very wrong huge valve gap, my guess and conclusion is as followed:
The scooter´s last run with "beloved hubbie" on the highway was with either the wrong oil and/or not enough oil, or a defect oilpump, therefore it got too hot and seezed the valves/valvestems in open position. Therefore the huge valve stem gap. And therefore no compression. Looking at the open cylinderhead I also do not notice or see as much motoroil as I would expect or I saw in this aerea on my scooter´s engine.
Also possible now is a temporary piston seizure or piston damage via open valves. An endoscope camera system might help for further diagnosis.

Long story short: In my opinion this engine is dead.

And I am always a bit sceptic, reading about John and Jane Doe´s talking about themselves how experienced they are and what they have managed to do already "successfully" on their vehicles.
According to what dear hubbie has done to the scooter so far and how Renee tried to do the failure analyzis, I would recommend to both of them that they should better leave this kind of "service and repair" to real world professionals and mechanics.
It´s cheaper for them and maybe safer for all of us. 

1) check if fuel line near tank on its way to the injector is squeezed somehow and somewhere. Might be an issue with very heavy riders.
2) check ventilation of gas tank cap. Try a testride without the cap eventually. Might even be a problem with heavy riders. Do not block the gas cap with rags or other luggage. Let it breathe a bit.
3) American Like scooter models have a rather senseless but complicated gas tank breather recycling system on board thanks to your overprotective safety board. Once this system was flooded by overfilling the tank, it might also cause issues.
4) healthy batteries are an absolute must for this electronically operated fuel injection system. voltage at rest is only one of three important figures. What figures does the multimeter show under load e.g. while pressing the starter button? Does it fall below 11.5 Volts? What does the multimeter show while idling or reving the engine a bit on center stand? It should significantly rise from 12,6V up to maybe 14V. Otherwise rectifier/regulator is malfunctioning.
5) was the first valvecheck ever done (and properly) on this scooter? If not, do it. 0.10mm both in and ex.
6) post here later what you have found out to make the scooter run again.
Good luck!

I experienced the same thing on the oem tires. They weren´t balanced and centered at all from factory. After I put on a set of new tires (different brand and thread) and BALANCED and CENTERED them very exactly, the wobble of the handlebar was totally gone. I now can/could ride handsfree up to top speed (~70mph). Like a train on its rails. That feels real´ good.

The combination of a certain constant amount of throttle and a well dosed use of the rear brake has always brought me safely through tricky slow speed passages and corners. Just keep practising. It´s getting better and better with every exercise. 

Should be....don't know what all the extra letters mean.
As long as it is a good quality, sealed both sides, 40x17x12mm.
I know for certain it is not Vespbretta's 6201!

Stig

The 6203 C 2HRS  is correct as for the rear wheel. The 6201 is smaller and for the front wheel!