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Author Topic: Tach way too fast...what would cause that?  (Read 1544 times)

Offline wicks

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Tach way too fast...what would cause that?
« on: June 12, 2017, 12:51:21 PM »
Tried searching on this one, couldn't find any topics. My tach reads almost double the speed the engine is turning. Steady and smooth, but far too high. 3,500 reads at 6K rpms. The bike has 7K miles original, all parts are original, and nothing was changed that could cause this problem to develop.

Any clues?

(73 V7 Sport)




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'77 LM1 / '93 1000s / '73 V7 Sport / '06 Ducati Paul Smart  / '73 Porsche 911s / '94 Porsche 964 Turbo / '94 Defender 90

Online pehayes

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Re: Tach way too fast...what would cause that?
« Reply #1 on: June 12, 2017, 12:59:14 PM »
Hah!  Be happy with what you have.  On my SPII, the tach has started to SPIN like a PINWHEEL at speed.  I've trying to get a video of it, but I can't seem to make it happen while sitting still.  Have to be running down the road.  Quite amusing to watch.

Patrick Hayes
Fremont CA
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Offline Old Jock

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Re: Tach way too fast...what would cause that?
« Reply #2 on: June 12, 2017, 01:13:33 PM »
I have no clue but it happened to me with an LM 1000

I thought I was losing my mind when it happened.

Just to let you know you are not alone

Hopefully somebody will come along who understands the innards of these things will chime in

John
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Offline RinkRat II

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Re: Tach way too fast...what would cause that?
« Reply #3 on: June 12, 2017, 01:44:52 PM »
 On a cable drive tach there is a specific gap between the drive magnet and the driven indicator. sounds like recalibration is needed to correct this. A good speedometer shop will do this.

   Paul B. :boozing:
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Re: Tach way too fast...what would cause that?
« Reply #3 on: June 12, 2017, 01:44:52 PM »

Offline wicks

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Re: Tach way too fast...what would cause that?
« Reply #4 on: June 12, 2017, 02:24:12 PM »
Oh interesting - like the spring has loosened up. I am a DIY guy generally - wondering if anyone has a reference on our gauges and what it takes to take them apart and make adjustments...
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Online Kiwi_Roy

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Re: Tach way too fast...what would cause that?
« Reply #5 on: June 12, 2017, 03:33:06 PM »
Is it a cable drive
or is it Electronic like my 72 Eldo?
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Offline wicks

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Re: Tach way too fast...what would cause that?
« Reply #6 on: June 12, 2017, 04:00:19 PM »
Mechanical - cable driven
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'77 LM1 / '93 1000s / '73 V7 Sport / '06 Ducati Paul Smart  / '73 Porsche 911s / '94 Porsche 964 Turbo / '94 Defender 90

Offline wicks

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Re: Tach way too fast...what would cause that?
« Reply #7 on: June 15, 2017, 12:36:11 PM »
No tips/resources on how to operate on the tach?
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