I know that suntour system is crap...but i just like everything original if possible...also im limited money wise in what i can buy....im not using electric bike every day as i use my Trek non electric bike most of the time....my brother wants my 22" vulcan as its too big for me...so he has bought me two secondhand 18" frames as the first one has been damaged by the courier and also the seller had drilled three holes in the cross bar to fit a battery...im just waiting now for the other frame to come which is completely stripped of any parts..but its in really good condition.
What are those metal rings for on the axles...are they just cosmetic ???also i noticed the bottom bracket should have a metal ring which stops the torque sensor from moving to prevent the cab le from being ripped out.
His photo shows that he is using a standard Chinese pedal sensor, not the Suntour torque sensor. Some of what's been discussed is a bit mixed up, so be careful. I'm pretty sure that if you want to use the Suntour chainwheel torque sensor, you need the stepped long bottom bracket that you showed.
Personally, I think you're wasting your time building up a bike with the Suntour stuff because there will inevitably be more problems down the road. The Suntour system is not bad when it works, but there's nothing special about it apart from its unreliability.