Well, mine was a bad speedo cable (Gemo brand). If you have a similar cable issue it's easy to detect. Pop the grease cap off, and the cable off of the speedo head. If you can turn it by hand easily, with pulsing or binding, then likely the cable is OK and the bounce is in the speedo head itself. They do tend to do that after 2-300K. You should make sure that the grease cap is on straight - as near perfect as possible - so you don't have an eccentric drive causing the cable to pulse.

Keith Hughes
'86 Westy GenV (Marvin)

 Date:    Mon, 24 Jul 2017
 01:00:51 -0600
 From:    Eric Wunrow <VW@ERICWUNROW.COM>
 Subject: Re: Speedometer Cable
 
 I just replaced the grease cap with a
 new one after the old square punch =
 hole finally went circular, and the
 bounce is absolutely identical.
 
 Seems to me all the VWs I've ridden in
 had the same tendency.
 
    Eric
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