Author Topic: Retrofit tacho to A7 Star Twin  (Read 1124 times)

Offline pdg

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Retrofit tacho to A7 Star Twin
« on: 05.11. 2014 13:52 »
Hi,

Does anyone know if it is possible to retrofit a cable-driven tacho to an A7 Star Twin?

I've seen timing covers with the requisite hole (assuming everything else fits?). Am I right in assuming that the tacho is driven off the magneto pinion nut and if so can the non-tacho nut I've got be replaced with one onto which a cable can be attached?

Many thanks, Peter.

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Re: Retrofit tacho to A7 Star Twin
« Reply #1 on: 05.11. 2014 18:34 »
G'day Peter.
 Is yours a long or short stroke? I'm not sure of the long stroke but the short stroke isn't a problem if you have manual advance. The extended nut is available, the g/box's and covers are getting pricy.  With auto advance the drag of the tacho/cable/g/box would restrict the unit from advancing, and you'd have to modify the nut.
Cheers.
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
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Offline pdg

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Re: Retrofit tacho to A7 Star Twin
« Reply #2 on: 05.11. 2014 19:30 »
Hi Muskrat,

Many thanks for your reply. I have auto advance but am thinking of getting rid of this with an electronic ignition upgrade. Do you know the part number for the extended nut?

Thanks, Peter.

Offline wilko

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Re: Retrofit tacho to A7 Star Twin
« Reply #3 on: 05.11. 2014 21:09 »
You will need a reverse drive 1:1 ratio drive to suit any 2:1 tacho.As long as the tacho itself isn't reverse driven And just to confuse you, a 4:1 tacho can be used if you use a 2:1 drive.

Online a10gf

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Re: Retrofit tacho to A7 Star Twin
« Reply #4 on: 05.11. 2014 22:03 »
Hello, have fitted a tacho system to my A10, made my own 'extended nut', and you'll need a tacho-ready timing side, or find a way to do a nice machining job on a non-tacho one.

A10 GF '53 My A10 website
"Success only gets you a ticket to a much more difficult task"

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Re: Retrofit tacho to A7 Star Twin
« Reply #5 on: 06.11. 2014 09:00 »
G'day Peter
67-713 = 67-0713
http://www.a7a10.net/forum/index.php?topic=3260.0
http://draganfly.co.uk/index.php/accessories-a-misc/product/14717-
Cheers
PS. I'm a electronic ign convert. Boyer on my 3 A's.
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Offline pdg

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Re: Retrofit tacho to A7 Star Twin
« Reply #6 on: 06.11. 2014 09:22 »
Many thanks. Does this simply replace the existing pinion nut?

Regards, Peter.

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Re: Retrofit tacho to A7 Star Twin
« Reply #7 on: 06.11. 2014 09:29 »
Yes
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
Australia
Muskys Plunger A7

Offline pdg

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Re: Retrofit tacho to A7 Star Twin
« Reply #8 on: 06.11. 2014 09:32 »
Brilliant. Many thanks.

Now I just need to find the timing case ....  *eek*

Offline pdg

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Re: Retrofit tacho to A7 Star Twin
« Reply #9 on: 06.11. 2014 10:41 »
Does anyone have a picture of the tach drive that bolts on the outside of the timing cover, please? Does it have a circular base plate the fills the entire recess in the timing cover or is it an elliptical shape that just covers the area between the 2 screw holes (whilst of course filling the hole in the timing cover)?

Many thanks, Peter.

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'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, .
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Muskys Plunger A7

Offline pdg

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Re: Retrofit tacho to A7 Star Twin
« Reply #11 on: 06.11. 2014 10:57 »
Many thanks - again!

Offline terryg

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Offline pdg

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Re: Retrofit tacho to A7 Star Twin
« Reply #13 on: 06.11. 2014 11:51 »
Many thanks. Have found a timing cover, so the process to completion has really started now.

Online chaterlea25

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Re: Retrofit tacho to A7 Star Twin
« Reply #14 on: 06.11. 2014 11:56 »
HI All,
I have found that the 1:1 tacho drive in goldies gives the rev counter mechanism a hard life
A  2;1 drive and recalibrated or 4:1 tacho is a lot more reliable
My 2 cent opinion
The 3:1 tachos driven from the oil pump are scarce and (even more!!) expensive  *eek*

Cheers
John
1961 Super Rocket
1963 RGS (ongoing)