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Tach for Magneto Ignition

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Post Sat Apr 22, 2017 5:25 pm

Posts: 49
My Indian Scout track bike has a Morris Magneto, and no other electrics. Last year I tried a Digital self powered Tiny-Tach, which has one wire that is wound around a plug lead, and an earth lead which I attached to the frame of the motorcycle.

The Tiny-Tach lasted all of about three minutes, good earth connection to frame, engine plates pulling up on bare steel not paint, I would have thought that was sufficient .

Has anyone successfully run a Tiny-Tach from a Morris Mag or any other Magneto?

Also Morris Magnetos sell a three wire Tach Module (Adaptor) for running an electric analogue style Tach, what I don't understand about the Tach adapter, is one wire hooks up to the 'Tach Trigger'. What or were is the Tach Trigger on the Mag?

I want to run a light weight self powered Tachometer, to help find my best torque output at unknown revs on my local Dyno, and from that sort out my gearing.

Suggestions welcome.

Post Sun Apr 23, 2017 6:09 am

Posts: 76
If you want lightweight, self powered tachometer, you can't beat the Scutsi tach.
One wire to plug wire is all that's required.
Lot of racers use them.

Post Sun Apr 23, 2017 12:20 pm

Posts: 408
Location: Bergen, Norway

Thats a neat one.
Have you tried this?

Have done reasearch into installing a digital tach to a magneto, and gotten no wiser.
Talked to these folks
Was planning to replace the cable driven Smith tacho on my KHR/XR with one of their replikas.
They could not help me as the software would not be able to handle the uneven firing at 45, 315deg etc.
They said at some point in the future they might get there.

Last edited by GuS on Sun Apr 23, 2017 3:45 pm, edited 1 time in total.

Post Sun Apr 23, 2017 1:14 pm

Posts: 135
Location: BRANFORD, CT

In vintage dirt track racing most of us are using a SENDEC teltale tac.
It is digital and only displays current RPM about every 5 sec.
This is not enough to read while your are riding but tells us max rpm on the track for gearing purposes.
Same could be applied to road racing.

Where to hook it up.
With a magneto this tac gives fuzzy operation with the wire wrap on the plug wire as do most dynos using a plug wire clip.
Best reading are gotten wiring to the kill button lead on the mag.
Because most v-twins use a wasted spark you can use the 2 stroke configuration.
Last time I got these they were about $80.
Bruce Argetsinger
AHRMA Dirt Track # 67J

Post Sun Apr 23, 2017 3:44 pm

Posts: 408
Location: Bergen, Norway
Great information. Thanks for sharing.

Post Sun Apr 23, 2017 5:52 pm

Posts: 49
Thanks for all reply's. I will try a single wire tach again, this time wired to the kill switch.

Post Sun Apr 23, 2017 7:53 pm

Posts: 76
Yes GuS,
I have this on my WR (works great) and about everyone road racing vintage bikes uses a Scutsi

Post Mon Apr 24, 2017 11:48 am

Posts: 408
Location: Bergen, Norway
Ralph. Thanks

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