DEFECTIVE SPARK PLUGS

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JEAN-NOEL
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DEFECTIVE SPARK PLUGS

Post by JEAN-NOEL »

Hello,
Last year the bike suddenly started to run on one cylinder. Swapping the plugs I found that one (N3C) was défective, so I ordered from AMOC Parts a set of N4C. No problem until yesterday : when I took the bike for a trip, it started 2nd kick, but immediately ran on one cylinder. I checked the plugs, and again one ot them was defective. So I made a short run with one N3C and one N4C. I tested the head temperature with a flash thermometer, and on both it was the same. Gap was perfect, no foul...but a bit rich. To avoid a breakdown I have ordered a new set of N5C, and also a set of B6ES.
Does any one has experienced the same problem ? Both N3C et N5C were new, from the club.
Thanks in advance for your advices !
Kind regrds.
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1608
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Re: DEFECTIVE SPARK PLUGS

Post by 1608 »

Hi Jean-Noel, can't remember where I got my Champion plugs from but, I experienced my first ever duff pug recently ( biking for forty + years!!!) on Ariel 650. The bike had stood for a couple of months and had been running rich. So, could just be a bit fouled I suppose.
JEAN-NOEL
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Re: DEFECTIVE SPARK PLUGS

Post by JEAN-NOEL »

No John, both are clean...rather black, but not sooty or fouled, nor oiled.
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GSAX1
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Re: DEFECTIVE SPARK PLUGS

Post by GSAX1 »

Spark plugs are very seldom defective; most likely you have an ignition problem. When the voltage is marginal the cylinder may fire when the plug is clean, but once it gets sooty the current will leak to ground through the soot. After all, soot is mostly carbon, and carbon is a very good conductor. With a healthy ignition coil that gives a sharp voltage spike the current jumps the gap before it has time to leak to ground.
g5wqian
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Re: DEFECTIVE SPARK PLUGS

Post by g5wqian »

hi jean-noel,
i use N5C in my ajs model 30 , but have also used AC 43XL , and used some nippondenso plugs which i dont remember the number for them but all good .

when i used N4C and also N3C i had fouled plugs unless i did long trips and because i tend to ride between 50 and 100 miles and not on a regular basis i find the N5C is much more suited to what i need and i dont foul the plugs .

i have not used NGK yet but i do have some B5ES and B6ES in my spares cupboard .

ian
Mick D
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Re: DEFECTIVE SPARK PLUGS

Post by Mick D »

Hi

I use NGK plugs on all of my bikes, not had a bad one yet.

Point of pedantry - fouled plugs fail because their resistance to sparking increases, carbon, (soot), does not conduct electricity, graphite does but it's not a product of combustion as far as I know.

Regards Mick
JEAN-NOEL
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Re: DEFECTIVE SPARK PLUGS

Post by JEAN-NOEL »

Just back from the shed...The two defective plugs are both perfectly clean and dark Brown. I got the idea to test them on the lawn mower...not a blue fat spark, but a spark ! The mag has been fully overhauled. Bike runs nicely with 1 N3C and 1 N4C. Engine is new, compression are OK, no smoke. What a mystery ! Now, i am waiting for the new sets of sparking plugs before riding far from my home !
raffles
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Re: DEFECTIVE SPARK PLUGS

Post by raffles »

Whenever I have a starting or plug problem I drain the fuel tank and clean the carb so far this has always
cured the problem. Its just the crap petrol we have now
Tony
Reynard24
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Re: DEFECTIVE SPARK PLUGS

Post by Reynard24 »

Crap petrol would be better than nothing - idiots panic buying again. Why don’t the BBC and newspapers shut the ***k up and stop provoking the morons to do their worst!
Mick D
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Re: DEFECTIVE SPARK PLUGS

Post by Mick D »

Reynard24 wrote: Fri Sep 24, 2021 8:19 pm Why don’t the BBC and newspapers shut the ***k up and stop provoking the morons to do their worst!
We could do our bit too, by not voting for the morons :roll: :(
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