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MG Midget and Sprite Technical - Squawking rev counter!!

Frogeye with the mechanical revcounter. Its started intermittently making a horrible squawking noise!
I thought it was the cable as holding and putting sideways pressure on the cable stops or changes the pitch of the noise. Fiddling with the knurled attachment knob, backing it off also temporarily stops or changes the noise for a moment or two, but it keeps coming back. I've tried 3 different cables and adjusting the route a bit but I'm no further forward.

I am a bit wary of tampering with the rev counter itself as otherwise its working fine, but wondered if there is any advice here?
GuyW

Internal lubrication needed? Could be a dry bush or gear. Something like a watch oil maybe, or at thickest, 3 in 1.
anamnesis

Yes, could try that. On the basis that the counter has had no maintenance since at least 1984 when it was last on the road, and very possibly none before that either 😱, it could have dried out a bit!
GuyW

They're pretty simple items and IIRC only one bit that spins with the cable. Once the bezel is removed the guts can be removed by undoing to screws that hold it to the case. It works the same as a speedo but without the complication of odometer and milometer.
David Billington

It could be the gearbox on the back of the dynamo. Don't ignore it. I did and it suddenly self destructed.
Rob




MG Moneypit

No, its not the gearbox, Rob. I checked that. I know they can be problematic and very sensitive to lubrication - wrong, or lack of!
GuyW

LOL !
It's turning into one of those jobs. "try a little oil", he said! To do so means removing the mechanism - which means removing the bezel (glued with the brittle black remnants of a sealant)
Then remove the glass ( half an hour to very, very carefully prize it out with a stanley blade)
Remove the trim ring (rusted in place)
Remove 2 screws at the back ( rusted but came out easily!)

Having finally got in just to apply a few small drops of light oil now to clean and reassemble. But first, what is a good paint to respray the reflective inside of the casing?
GuyW

Guy,

That "sealant" should be an O-ring. Are you sure that it is sealant and not a very old deteriorated O-ring? They do tend to resemble sealant with age and since you don't know if it has ever been apart, that's what it might be.
Martin

Yes Martin, there were thin O rings either side of the glass but also this black brittle stuff in the back of the chrome bezel. I've seen similar on other cases so I think its original.
GuyW

Guy

Your right it is a black sealant. It was used to seal the front chrome ring on. It goes rock hard over time and is a devil to remove.

I was never able to find the correct paint for the inside. Its a sort of reflective light blue. I sprayed mine with a matt white and its fine.
Bob Beaumont

The later electronic tach also has a painted light blue part. I used some Humbrol model paint (no. 47, sea blue gloss), brush applied. Small 14ml tinlet as you don't need much.
Bill Bretherton

Ah good idea Bill. never thought of that!
Bob Beaumont

The mechanism is identical to the speedometer. Last week I was off to the first show of the season at Thruxton and had exactly the twittering squawk that you describe. On arrival I removed the speedo - no tools required just fingers - squirted the customary WD40 into the drive spindle, and all was well. Lying on my back with my head in the footwell caused some amusement.

It could have been worse. Many years ago my own culpable neglect caused a speedo to seize solid, breaking the drive cable. Like an idiot I bought another one. Much later I realised the old one was salvageable. It just needed to be lubricated properly. It made a tidy profit on eBay.

If you are interested, you might consider changing to an electronic tacho. Here is my video on butchering a modern instrument to fit the entrails into the Frogeye case.

https://www.youtube.com/watch?v=OEOIq9qf4A0
Les Rose

Yes Les, I could probably have just dribbled some light oil into the bearing without dismantling. But when removed from the dashboard it was rattling loudly with something loose inside the casing. When eventually dismantled the rattling was a glass orb of a bulb!
GuyW

So the DPO replaced only part of a burned out bulb. Sounds like he couldn't be bothered to do it the right way.
Martin

Not even sure it was burnt out, Martin. The glass was intact but had broken off the metal base that is a push fit into a hole in the back of the casing. So it had ended up wandering freely around inside amongst the spinning bits of the tachometer. Dangerous place to be, it could have hurt itself.
GuyW

This thread was discussed between 04/03/2023 and 07/03/2023

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