wire diameter on most is 4-5mm depending on stiffness
GY6 50 and the big ones
Inner diameter: 48.5 mm
Length: 154 mm
The shitty China "GY6-50" but really QMB139
Inner Diameter 49mm
Length: 106mm
Zuma/Jog Minarelli
Inner Diameter:44.0mm
Length: 108.0mm
Zuma 125 4strokes
Inner Diameter: 54.5mm
Length: 116mm
This site has a lot listed