Very nice bike. I got a 1983 Yamaha YZ490 for $150. I am trying to create a Broc Glover Replica. I removed the engine, split the cases (oh boy did I get lost in the gear box), I am about to Paint the Motor and then button her all back up. I have to get some White Side Panels.
I really like your bike. The 1984's have more in common with the newer YZ490's. Mine has the offset Exhaust Mount where as yours is a Center Exhaust Mount on the Cylinder thus you can use any 1984 thru 1989 Cylinder where as I only have the option of the 1982 and 1983.
Once again Very nice bike.