Wing tips #4

Tips and Recommendations from Guru Mike Nixon

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mikenixon
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Wing tips #4

Post #1 by mikenixon » Wed Feb 14, 2018 11:01 am

The peak volt adapter
In the dark ages of motorcycling, shop mechanics relied on resistance tests for checking out ignition components, specifically the ignition coil and its partner the pulse generator (or trigger). However, ohmming has never been a good way to test an ignition coil and it's no better a method for a pulse generator. Savvy techs learned to test both of these parts dynamically, that is, while they were working. The ignition coil by simply rapidly powering it on and off, and the pulser by connecting to it an analog multimeter set for uA (pico amps) and watching for a subtle needle twitch. Kind of a homemade megger. Much better than ohmming, officially endorsed by the Yamaha factory, and the method I prefer even today. An even more advanced method of testing a pulser is to use a 9v battery to substitute for the pulser, attaching it in the bike's harness. Very effective, and I sometimes use it as a backup to the twitch test. But these comparatively, innovative, alternative, and though uber-effective rather guerrilla mechanic methods have never been widely known, so another method eventually came to the fore, one endorsed by all manufacturers and now included in the current OEM manuals. This is the peak volt test.

You'll recall that the ignition coil's two windings-- primary and secondary-- cross induce. That is, after the primary has induced the secondary, the secondary in turn reinduces the primary, and the two actually go back and forth, until the energy is spent. This backlash effect back to the primary is very predictable and some geeky wag somewhere came up with the idea of testing the health of the whole ignition circuit by measuring it. Today's OEM manuals list voltages that can easily be read at the primary of between 150 and 300 volts. A reading that is out of range of the manufacturer's published spec will indicate that further tests to pinpoint the trouble need to be performed.

Interestingly, the peak volt test's greatest contribution from the standpoint of learning, is that it is a direct indicator of the speed of the primary winding's collapse, and thus the condition of the transistor inside the spark unit. When collapse is sharp, the transistor's break is clean. The peak volt test then, aside from its diagnostic value, is the best indicator of the spark box's function. It's a verifier of the speed of collapse.

Get a peak volt adapter (designed for digital multimeters) made by a very innovative American company called ESI on Amazon. The Big Four also sell their own version, made by Kowa in Japan.
Mike Nixon

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desertrefugee
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Re: Wing tips #4

Post #2 by desertrefugee » Wed Feb 14, 2018 12:11 pm

Hey Mike,

Genuine thanks for the continuous stream of great and, as in this case expecially, extremely thought provoking articles. As a recently retired EE, this one struck a nerve. So much so that I might even see about cobbling up a "quick-n-dirty" latching peak detector circuit - complete with $2 Chinese display - just for fun.

For the record, I've archived off-line every installment you've offered up in this series. They are eagerly anticipated.

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mikenixon
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Re: Wing tips #4

Post #3 by mikenixon » Wed Feb 14, 2018 6:49 pm

Desertrefugee, thanks for the feedback. Appreciate it! :)
Mike Nixon

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gltriker
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Re: Wing tips #4

Post #4 by gltriker » Wed Feb 14, 2018 11:34 pm

You must recall the Merc-O-Tronic Ignition Analyzer, Mike? ;)
In 1972, when I started professionally repairing chainsaws at an I-H farm equipment dealership in Syracuse, a Model 88 Merc-O-Tronic sat on a shelf, at eye level over the workbench. Totally unfamiliar instrument to me, though.
With a little training from an old timer, and ignition service data from McCulloch and Homelite, it became a valuable tool.
I used that machine every time I performed any breaker points magneto ignition repair, for 7 years.
( Electronic, Solid State or whatever else you may call it, ignition was not in the picture in those years.)

Anyway.... in 1979, I went to work for a TORO Company Distributor and requested a Merc-O-Tronic Ignition Analyzer for the McCulloch products they also distributed. I believe it was the Model 98 at that point. Along with the base unit, it came with 2 different adaptors for Electronic, Solid State or whatever you may call it, ignition.
In my new role as a McCulloch selling/servicing dealer support contact, I rarely ever used it. Never, ever, used either one of those 2 adaptors. :IDTS:

After reading this excellent Wing tips #4 article, I reckon those 2 Merc-O-Tronic adaptors were peak voltage testing devices.

Although I'll most likely never utilize one of the peak voltage adaptors you have detailed the purpose of, perhaps I'll get one off Amazon to add to my toolbox, too.

Thank you, Mike! tumb2

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mikenixon
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Re: Wing tips #4

Post #5 by mikenixon » Thu Feb 15, 2018 10:06 pm

Hey, gltriker, thanks for adding more perspective. Great! Look up Imrie ignition testers, Australian-made, back in the 80s an authorized Honda tool, though I don't think it was peak volt. More low and high voltage. Just reminded of it with your McColloch experience. :)
Mike Nixon


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