So my 88 K75S had a couple of instrument cluster issues. The tach didn't work, the neutral light didn't work, and the gear indicator didn't work.
I removed the cluster, and found light greyish corrosion on several areas along with a few burned out lights. I carefully hoses everything down with DeOxit purchased at my local Guitar Center. Radio Shack didn't have it. I had to let the components sit around for about a month. I doubt that had anything to do with it but it happened. I put it all back together tonight and everything works!!! Tach, Gear Indicator, Neutral light! I'm so stoked!!!!