Tach Noise

After not having a tach for years, I fixed the lower drive unit by extending it a bit so that it would mesh with the drive itself. With a good original cable the tach worked great for about 10 miles, then the needle started going haywire and a nice screech emanated from the tach area. It was intermittent for a few miles, then I disconnected the cable at the tach. No more noise now, so I assume it;s the tach itself. It looks like new, so what could be wrong? Surely, 39 years of sitting and occasional use couldn't be the problem! Do you lube these things? Send them out for repair? Guess at the rpm's like I've done for years?
Any good answers will be appreciated.

Thanks for the help! Steve

No lube goes inside the clocks which should not make any noise so 1st suspect is drive pushed cable too far into the clock &/or the drive/cable has ground up but clock still ok. Clock end of cable should end up flush to the cable end nut rim when pulled to end of cable stop.

Run the tach from a drill, that`ll isolate the source of the problem some.

Do you lube these things?

affirmative . removeing forign matter is a preliminary . Lube can coagulate . tach's Manetic . pretty basic but finely balanced device .

Possible to gently pry the bezel off , with a smooth flatish lever or two , working round at least threetimes on the lip .

How to break into a smiths ( or Vegilia ) Tachometer .
http://www.gomog.com/allmorgan/smiths_t ... ersion.pdf

Thanks for the advice--I finally solved the problem by first shortening the cable a touch and then giving the tach a tiny drop of WD-40. Probably shouldn't lube it, but it worked. A quick way to check the tach for a noisy problem is to use the tapered square end of a file, insert it in the tach and spin it with your fingers. This pointed me in the direction that it was in need of a little lube.

Have a great day!

Interesting fix. I have a Smiths Speedo with 26000 on it that has a sticky needle that goes spastic on the drill check. Staring into the instrument light hole shows desert bone- dry internals. Thinking about a fine oil similar thinking as WD 40 is a penetrant not much of a lubricant ,gotta try something , right ?