assuming you still have original solenoid. positive wire to a momentary switch. wire from switch to solenoid. stock solenoid has 2 wires on it, does not matter which, but 1 needs positive from switch and other needs ground. normally grounds through neutral switch, just run to battery negative.
if original solenoid is gone. run an 8 gauge wire from battery to starter. cut wire somewhere accessible and install a heavy duty switch, available at auto parts store. obviously you need ground going to engine as well
Trikes: All Honda: 84 250r, 85 86 and 87 250sx, 84 and 85 125m, 79 82 84 and 85 110's, 73 us 90 and 77 atc90, 75 atc70
Cycles: Honda: 71 cb100, 78 cb750 coming soon cb750 trike. Yamaha: 67 yds 3 (250cc, 2cyl, 2 stroke), 82 750 SECA
Other toys: Chenoweth VW sandrail dune buggy, old race go kart, racing mower, 76 Arctic Cat Pantera 440 snowmobile
KEEP IT ON ALL 3 OR AT LEAST 2 AT A TIME