Aprilia sr50 morini rear wheel nut ?

Hi all and sorry if this is in the wrong place.
Just asking if anyone knows the (morini engine) rear wheel nut size or know how to get measurements.
I cant find any info on it as it only comes up with sizes for the (piaggio engine) and that nut it too bit.
I had one but rolled down a drain and its lost forever lol
Any help appreciated.

 

Measure the diameter of the threaded shaft and threads per inch, or use a thread pitch gauge then off to a nut/bolt supplier !

 

Minarreli/Yamaha engine is 22mm

 

Thank you both.
Ill try figure out how to do the measuring ect.
Im not sure if the minarreli has the same size wheel shaft. I wish all aprillia engines used the same sizes as they used piaggio/ minarreli and morini engines.

 

My bad, thought it was a mark1 Aprilia SR

 

No worries mate.
It was a aprilia sr50 R with the piaggio engine but was completely fooked so swap it out for the morini engine but lost the rear wheel nut lol
Its so sad dropping somthing and litrally watching it role down a drain. Reflexes didnt kick in quick enough to grab it.