Single 50A vs dual30A (60A) breaker

[tonyiiiafl]

Final chapter on my Kohler 6.5CZ genset. Looks like the previous owner removed the dual 30A=60A circuit breaker and replaced with a single 50A breaker. I found the proper breaker and was ready to install. Now remember I have NO ID plate on this baby to reference with confidence the spec version. So now I have both LINE leads from the gen head going to a single post on the breaker, and both load wires sistered up on the line side. The neutrals and grounds are set fastened to a single post on the unit. in this diagram, there is mention of a jumper wire from the line leads in some instances. However, there is also a scenario of NO jumper also. A bit confused as to how to proceed. In regular wiring it looks like a 220V system as the neutrals and grounds are sistered together. This denotes a 220V system. How can I determine this? Place a meter with one probe on the line side and one lead at the ground?

0A24BA80-1B0D-4EEB-9212-F5A460E8F018.png

0C57F6A3-EE6D-45E7-A913-111D94010E1C.jpeg

E583A975-F663-4453-B2B6-1D099D0D0A33.jpeg

A2473B4A-9075-4774-980D-ED936866D528.jpeg

346E8E52-5D86-469D-BEB0-49877FB23B87.jpeg

[tonyiiiafl]

OK, just placed a meter on between the sistered up line leads (photo 3) and the sistered up neutral/ground leads (photo 4). I am getting 123V on my meter. SO I am assuming it is a 120V system and requires the jumper as per in the wiring diagram?