Tach unstable

[gnflyn]

I have noticed that my tach needle seems to bounce around a bit at cruise rpm. Any advice on lubing the cable? Or perhaps a new cable? Thanks

[astjp2]

Re: Tach unstable

Just lube it...unless its bound up or broke, why replace it? Tim

[gnflyn]

Re: Tach unstable

what is best lub?

[astjp2]

Re: Tach unstable

Go and find a speedometer shop, they use a real weird grease, if not then just about anything that is like aeroshell 5 would work

[Pearson]

Re: Tach unstable

Graphite is best. Look at inner cable to determine which direction it is wound. The windings around the inner cable form a bit of a screw action, which pulls the graphite up into the cable.

[gnflyn]

Re: Tach unstable

Picked up a tube of Dorman graphite speedometer lub at O'Riellys for $2.99. Is it recomended to remove the cable and flush housing out with a cleaner such as Electroclean spray, and then reinsert cable lubing as you go? I know that cleaner is not supposed to leave any residue.

[astjp2]

Re: Tach unstable

Yes, cleaning would help...Tim

[Marv]

Re: Tach unstable

A can of Break Clean will do a great job cleaning the cable also, and its available at O'Riellys, Auto Zone etc.

[astjp2]

Re: Tach unstable

The Walmart house brand brake clean is some of the best stuff I have found, it doesn't leave any residue either....Tim

[gnflyn]

Re: Tach unstable

I pulled inner cable and it was coated with something looked like wheel bearing grease that was old and tacky. Cleaned it off and lubricated with speedometer lub. Test flew today and it still is surging, mostly above 2000 rpm. I did not remove outer cable housing as getting to the tach drive connection is most difficult.
Am thinking I will pull cable again and try to pull a cloth swab through using a thin flex cable, after I bite the bullet and disconnect at the tack.
Anyone have other ideas or options??? Thanks

[gnflyn]

Re: Tach unstable

I pulled inner cable and it was coated with something looked like wheel bearing grease that was old and tacky. Cleaned it off and lubricated with speedometer lub. Test flew today and it still is surging, mostly above 2000 rpm. I did not remove outer cable housing as getting to the tach drive connection is most difficult.
Am thinking I will pull cable again and try to pull a cloth swab through using a thin flex cable, after I bite the bullet and disconnect at the tack.
Anyone have other ideas or options??? Thanks

[M Towsley]

Re: Tach unstable

The old tacky grease is still inside the outer cable. That needs to be flushed out, and clean the cable again. PITA but needs to be done. Other than that, I haven't a clue.

[Pearson]

Re: Tach unstable

Do you have a right angle drive on the back of the tach, or does the cable go directly into the back of the tach? If you don't have the angle drive, and there were no frayed places on the cable, it is probably the tach.

[gnflyn]

Re: Tach unstable

Okay, super advice thus far. I pulled cable and disconnected outer housing at tack right angle drive. Flushed and lubed housing, cleaned cable in solvent. relubed everything and reassembled. Test flight, tach is noticeably better, but still bouncing some. I noticed tach cable is worn some about 3" from engine end, where it makes sharpest bend. Measured cable overall length at 43 1/2". Is this a stock cable or need a custom made one? If so, best place to buy one, and should that fix things? Thanks.....

[astjp2]

Re: Tach unstable

spruce