NO - unless it will start and you can test ride it. A good running 87 trx250x is worth about $250. For salvage it's worth about $50 to $100.
Why does it need a wiring harness? What happened to the one it had? There's no battery so there is almost no way to "burn it up". A new wiring harness is not available from Honda and good luck on finding a used one. If you want it to ride, it's not worth it, but if you need it for the parts or want to take a chance on parting it out....... You decide.