Re: crank arms spinning with sbp jack shaft kit
Check/rebuild your actual bottom bracket, the "Crank Bearings" as you say- I bet this will remedy your issue.
Also did you use the crank spindle that came with your kit? If so, you would have had to break open and dis-assemble the bottom bracket and should remember what kind of shape your bearings etc were in.
Good luck, I also just built up an SBP shifter equipped bike and it is an awesome enhancement to my bike. It's essentially a micro motorcycle now, as I'm certain you are finding out.
1978 Vespa Grande, 1984 JDM Honda Runaway
Firebelly Built 1985 Schwinn Sierra HT 67cc W/ Puch 50cc Cylinder Head, SBP Shift Kit, Pypelyne Exhaust, JNM Velocity Stack and Hi Flow Filter
STOP BUILDING MB's ON WALMART BIKES!! I MEAN IT. DON'T MAKE ME COME OVER THERE.