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Ibayorkie's D1
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Stoo63
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June 29, 2020 - 7:33 pm
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The chronometric is a "jerky" speedo by nature. Probably why they went over to magnetic speedos.

'52 D1 direct lighting plunger; '58 Square Four (project); '55 D3 Battery; '59 D1 direct lighting plunger;  '59 Tiger Cub; '60 5TA;  '76 FS1-E '97 Honda Sky SGX50.

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lbayorkie
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June 29, 2020 - 7:49 pm
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Thanks. I was actually reading a previous post just now which made that point. 

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Alan.Moore
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June 30, 2020 - 12:19 am
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Stoo63 said
The chronometric is a "jerky" speedo by nature. Probably why they went over to magnetic speedos.  

I think they went to magnetic because they were significantly cheaper to make than the chronometric and motorcycle (and car) manufacturers in the sixties were looking to reduce costs.  Just have a look at pictures of the parts needed to make a chronometric 'clock' mechanism and those that make up a magnetic speedo. The change took place around 1964 but the Police still used 'calibrated' chronometrics well into the 70's. 

The jerky nature is because the Chronometric 'clock' mechanism 'records' the speed input every 3/4 second and resets the needle to the current speed.

I've rebuilt a few and they really do not like any grease inside them. If the drive cable is over greased it does work its way up the outside of the drive spindle (between the spindle and the cable attachment tube) onto the worm gear and then gets thrown onto the clock mechanism. The drive gears do not need anything other than a smear of grease.

In most cases a good clean and light oiling at the required places with 'clock' oil is all that is needed. This is a good article thats explains what to do 

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Cheers

Alan

1939 Ariel VH, 1942 Ariel WNG, 1951 Triumph 6T Thunderbird, 1970 BSA Bantam B175, 1980 Honda CB250N, 1986 Yamaha SRX600

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lbayorkie
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June 30, 2020 - 7:23 am
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Thanks. I was reading a previous post which details overhauling of the D shape speedo, but I look forward to reading the article you provided in your link.

Alan

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Number6
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July 2, 2020 - 12:13 am
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Sorry wasn't on last page. But here's a video of one in action.

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Mike H --

Murphy's 4th law of motion states that any small object that is accidentally dropped will immediately hide itself under a larger object.

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Blue Heeler
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July 2, 2020 - 12:47 am
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Sounds like a cross between a knackered singer sewing machine and an old jet engine firing up. Video maker can expect a fixed penalty notice through their letterbox if they were in a 30 limit when they did that 🙂

So most of the noise from an early Bantam doesn`t emanate from the engine or exhaust? 😉

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Number6
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July 2, 2020 - 1:30 pm
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Well obviously he was using a variable speed drill to drive it, which can do anti-clockwise

I've done same using my Bosch mini power driver only does one speed tho, clocks about 25 mph I think

Mike H --

Murphy's 4th law of motion states that any small object that is accidentally dropped will immediately hide itself under a larger object.

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