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Flying my SA-100 now with 70 hrs today, my Tachometer RPM started oscillating fluctuating, jumping back and forth approximately 200-300 up and down? It as well as my other airplane all have mechanical tach's, and they as well as this one have been rock steady at idle and at cruise RPM they are the S&W or AC recording type. The rpm/engine is not surging, nothing out of the ordinary changes when I see the tach jump, but is a bit disconcerting when one is used to seeing steady idle, 650, run up 1750, and 2500 cruise RPM. My thinking is either the tach itself has in issue? Or the cable needs lubrication although I am sure I did so when I put it all together? Or the possibility cable drive end couplings are slipping in either the tach, tach drive on the engine, or the 90 degree angle drive? I have several other tach's and cable as well as angle drives to try. But thought others may have some idea of what to look for or try regarding their experience with similar issues? The tach has 70 hrs since it was new, but it is old stock and something I acquired with the airplane project that was started in the early 80s, and may be older than that, and was probably bought in the mid 80s and well over 30 yrs old! However the tach on my Starduster Too is every bit as old and still works just fine. Dave
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