I have the same bike, an 86 Diamond Back Apex in red. Nice to see yours still has the original Suntour Beartrap pedals. This was a top-of-the-line mountain bike in 86. A Tange double butted frame, a lugged unicrown fork w/ rack mounts on the fork blades, Suzue sealed cartridge high-flange hubs, a reversible stem, a spare spoke holder pulling double duty as a chainstay protector...what's not to love? This one looks like an early 86. Later in the year Diamond Back changed to Shimano XT thumb shifters that allowed for both friction & indexed shifting.