Good ole alignment issues... The clutch 'may' not be out far enough on the shaft(it appears to me its right up against the motor). Loosen end bolt on clutch hub, and the 2 lil allen bolts on otherside of clutch holding assembly to shaft. Slide whole assembly(clutch), away from motor until chain linesup straight. Tighten 2 lil clutch retaining allen bolts/screws, slug end bolt... DO NOT CRANK DOWN... just 'snug' inertia will hold it in place as long as u tighened the 2 allen bolts/screws TIGHT! From there its just a matter of tightening the chains slack. Loosen 4 bolts under motor, slide motor to front of kart(imo, leave just 'alil' play in chain...'maybe' 1/4in-1/2in.). If u slide it all the way up n still loose... you may need to shorten the chain.
Asfar as the brakes, if ur notta 'online' shopper... U can probly get wut ur needing, 4inch band for band-brakes, from ur 'local' lawn n garden tool supplier. Not like home depot or Lowes... We have alil mom n pops shop here that sells high end lawn equiptment/parts... evidently karts n some mowers have simular interchangable parts. N probly more knowledge of 'local' distibutors, if they dont carry.
This is just my observational opinion. Facts may vary from what Ive stated... but it IS just an opinionated hobby...
...1 mans trash...