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Author Topic: Easy DIY spark plug terminal  (Read 102 times)

Adirondack Jack

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Easy DIY spark plug terminal
« on: September 03, 2020, 02:10:55 pm »
After a bout with the infamous intermittent spark caused by the black rubber spark plug boot used on the recent M91 engine jumping around, I decided to go old school.
Though I’m sure a more elegant solution exists, I was in no mood to search, and used what was at hand. That turned out to be a couple of short pieces of telescopic brass tube, 1/8 and 3/32 OD.
After flattening one end of the 1/ 8 brass tube fully, the flat end notched with a Dremel cut off wheel, then opened up and a round notch filed on the inside of the jaws of the fork.  Once I was able to push fit the forked terminal onto the groove in the spark plug, I inserted the 3/32 brass inside the 1/8 brass, and cut it to length.  Instant snap on fork terminal.  If I’d wanted to get fancy I could’ve soldered the terminal onto the high tension lead. But today being a very bad glaucoma day, I just crimped it on. In any event it’s a solid connector, eliminating future rounds of “why the heck won’t this thing stay running, and why does it sound weak?  Turns out, weak and intermittent spark is no bueno.


70Rcode

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Re: Easy DIY spark plug terminal
« Reply #1 on: September 13, 2020, 05:57:23 am »
Technically correct (loose electrical connections are always bad, right ?) , But not always when a secure, fixed, Small gap within a Transparent spark plug boot can be very useful in diagnosing engine starting or running issues. The Jin ignition modules produce such a huge excess reserve spark voltage, that can be used to instantly & visually verify you deff have good normal spark Delivered to the plug or not as other mechanical probs can exist...Tom. 

70Rcode

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Re: Easy DIY spark plug terminal
« Reply #2 on: September 13, 2020, 06:47:06 am »
Strange how you miss noticing the obvious sometimes ....I didn't realize 'till now that the M92's come with the Black spark plug boot ! ...I had previously only seen transparent clear heat shrink tubing or plug boot Jin models & never noticed the Black boots 'till now !

Adirondack Jack

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Re: Easy DIY spark plug terminal
« Reply #3 on: September 13, 2020, 10:55:00 am »
The black rubber boot looks better to my thinking, but seemed not to grip the plug as well, leading to  Things moving around, and that secondary spark. While it is true these engines will make enough spark to spark in both the plug gap and outside the engine at the same time, when they do, it makes the resultant firing “soft”, audibly weak and leads to double or triple taps as weak firing fails to speed up the flywheel smartly.
This I learned for certain when I got errant secondary sparks using the brass terminal. So I wrestled the black rubber boot over the terminal and snapped it in place properly. The rubber insulated and stopped the secondary spark.  Immediately what had been a sorta mushy double tap run became a robust single tap With a long coast between taps. For the first time, it sounded like a big hit and miss. Note. I’m running the original governor springs, but they’ve been stretched some.

 

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