I am not a pro on these bikes and I'm not sure on how the K0 tacho is mounted but the tachos on newer models (K1-K7) are quite sensitive to vibrations if there is something wrong with the tacho rubber mountings.
My K5 tacho behaved exactly like your's but my problem was a worn crank making the bike vibrate more. I would check the rubber mountings before I opened up the tacho.
We have K0 experts on the forum and it will be interesting to hear their view on this.
[attachment=0:3hei5zzm]450 Ko Speedo-tacho.jpg[/attachment:3hei5zzm]
Greg, I had a very detailed write up from VJMC on repairing the tach, but it looks like working on a Swiss watch. It can be done though, but the write up made it look like it was not intended to be serviceable.
I will need to search for it online, but I do have it printed at home, some where.
Thanks John. I'll look into it. I had a great breakthrough today on getting the bike to run better. Turns out the float needles valves were worn which caused the cylinder to run rich. Replaced the float valves, cleaned up the carbs and reset float level. Runs like a top! Here are a couple pics.
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