I just watched your video, and something's not right. It really sounds like it's only running on 2 cylinders instead of all three. It's not very smooth running and you can easily hear every single time the engine fires, which it isn't supposed to be so easy to do with a 3 cylinder engine.
I found another video of a 1772 and it sounds a LOT smoother running and you can't determine each time a cylinder fires.
https://www.youtube.com/watch?v=D7TQggZxW9o
I'm not a diesel expert but I would say that something is preventing one of the cylinders from firing.
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'70 107 with k301 engine swap
'71 106 with 38" deck
'70 147
R with factory replacement k321, 42" deck
'61 Original with 38" timed deck
'63 70 "pinkie"
1863 with 54" deck
'46 Farmall H, '50 Farmall Cub
105 x2 (parts)