Potje

Hi D,

Mega/Picco plug are indeed different from Nova based plugs.

Don't know if I can explain it properly but I'll give it a try.
The thread of the Mega/Picco plug stops about a millimeter before the conical part of the bottom of the plug. The thread of the Nova plugs runs al the way down therefore the Picco plug will fit the Nova combustion chamber. This is because the thread in the Nova combustion chamber also goes all the way down so it doesn't matter if the thread on the Picco plug stops earlier or not. However, in the Picco combustion chamber, the thread stop about 1 millimeter before the conical part. And as the Nova plug needs thread all the way down to the conical part to seal the combustion chamber properly, it wont fit correctly.

I've attached a picture. The left plug is Picco, the right one is Nova. As you can see, the thread of the picco stops about a millimeter before the conical part.

Hope I'll explained it so you have an idea how it fits in the combustion chamber.

Regards,
Maarten