Rev counter reads very high

SteveBorland · Oct 24, 2014

Hi all, a quick question here. The Smiths rev counter on my 850 MkII reads very high. Idle (probably 1200-1500 by ear) shows around 3000!

I seem to recall that if the rev counter cable sits too far into the instrument, this can cause problems similar to this?

/Steve in Copenhagen

L.A.B. · Oct 24, 2014

SteveBorland said:
I seem to recall that if the rev counter cable sits too far into the instrument, this can cause problems similar to this?

Possibly? How far does the inner protrude? It shouldn't be more than 9/16" (7/16" for pre-'71 instruments)

Jose Refit · Oct 24, 2014

SteveBorland said:
Hi all, a quick question here. The Smiths rev counter on my 850 MkII reads very high. Idle (probably 1200-1500 by ear) shows around 3000!

I seem to recall that if the rev counter cable sits too far into the instrument, this can cause problems similar to this?

/Steve in Copenhagen

Steve,

If it used to read ok before then the spring controlling the needle may have weakened so the spinning magnet pulls the needle around more at the same rpm. Some voltmeters have an rpm facility so you could check the actual engine speed,

Jose.

Anglophile · Oct 24, 2014

Has it always revved high? My tach reads correctly when the temps are above 70 degrees Fahrenheit. It's all over the place below 50 degrees. It'll read as high as 7,000 (really 4,000) when the temps in the forties.

acotrel · Oct 24, 2014

I sometimes wonder if my rev counter is reading high, it's a worry if you always try to change gears before 7000 RPM.

SteveBorland · Oct 27, 2014

Thanks for the replies. Actually I don't know if the rev counter is faulty or not, this is the first time I've tried connecting it. It's on the list of things to do this winter.
/Steve.

tomspro · Oct 27, 2014

before you put a lot of time/money into to old analog device, you should at least consider getting one or both of these:

http://www.smithsgaugesusa.com/

Love mine.
Big bonus is eliminating the two ugly cables.

Nater_Potater · Oct 27, 2014

It's also possible that oil has migrated up the tacho cable. If it gets between the rotating magnet and reluctor cup, it'll start acting like the torque converter in an automatic transmission.

SteveBorland · Oct 30, 2014

Hmm. If this has happened, is it possible to clean the instrument without opening it?

/Steve, currently sitting in Kiev.

Rev counter reads very high

SteveBorland

L.A.B.

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Jose Refit

Anglophile

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SteveBorland

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