I would inspect the wire harness for cut wires and perform the resistance and continuity tests on all modules.
It’s a little hard to tell if the reg/rec is bad i think the only thing the book says you can do is check for shorts?
Does this quad have a good battery?
Have to be careful with parts swapping—several 88-89 (-93) electrical components are not interchangeable with earlier models. Revolution Research Line system. Aftermarket and used parts sellers often don’t make those distinctions
https://www.hondaatvforums.net/forums/honda-fourtrax/115625-86-89-350-foreman-differences.html?amp=1
It’s a little hard to tell if the reg/rec is bad i think the only thing the book says you can do is check for shorts?
Does this quad have a good battery?
Have to be careful with parts swapping—several 88-89 (-93) electrical components are not interchangeable with earlier models. Revolution Research Line system. Aftermarket and used parts sellers often don’t make those distinctions
https://www.hondaatvforums.net/forums/honda-fourtrax/115625-86-89-350-foreman-differences.html?amp=1