it looks like they used a 84 or 85 200x swingarm that the adjustment is up front by the pivot bolt. the brake rotor.hubs and wheels look like old 200x parts. you could weld the back of a 86 or 87 swing arm to the one on the trike. or get it from any atv with the normal bearing carrier you turn to adjust the chain. that chain tensioner looks like one off the universal ones you can buy that will fit any bike.
JASON LISKEY
1985 atc 250r ---- finsh line axle,.fmf exhaust and rictor privateer silencer, prm grab bar.
2008 KTM 525xc quad ----- HMF exhaust, HRE chromoly stem,
86 trx 250r --- with after market chromoly frame and everything else done to it
01 400ex --- with 86 trx 250r motor
87 250x + 93 300ex both 350x powered
2 = 86 atc 350x's
86 atc 250r
83 atc 185s --- from retired guy not ridden since 87
Bandito framed 110 with 85 motor and yellow us90 fenders + tank