The 83 threw 85 motors are pretty similar, The 84 - 85's where not the fastest bikes stock. The hot trick in 84 was to swap back to the much faster 83 top end parts (cylinder/head/reeds/piston/power valve) but thats an advanced mod. The 85 is pretty much in most ways identical to the 84, the slight changes or mainly in the minor chassis changes between the years. If you bike has a cable running down to the rear brake pedal just disconnect it. It's was yamaha's failed attempt at brake activated suspenion system. It didn't work suppose to soften the suspenion for braking bumps but it worked all the time you hit the brake even when ya didn't want it to. I rode CR's around this time though :)