Author Topic: spark plug query  (Read 772 times)

Offline chaz

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spark plug query
« on: 24.07. 2013 17:16 »
running a pair of plugs , both replaced recently.
found out whilst riding that only the right hand was firing , got back to the garage, dried out left hand and started, both ran for a short while. I was guessing its setting up new carbs....
now it seems that when plug cap is loose left pot fires as it should.
as its a single coil with dual output and boyer ignition have I a dodgy cap or a duff plug??
presumably Im being misled with fuelling as if plug isnt firing then fuel wont get burnt hence wet plug. must be firing somewhen as left hand pipe is hot but not as hot as right  *conf*

thoughts please
allways willing to learn
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Offline A10 JWO

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Re: spark plug query
« Reply #1 on: 24.07. 2013 17:45 »
I submitted a thread on plug problems this year, all the experts joined in. It was headed " NGK or Champion". Lots to read.

Regards Colin.

Offline chaz

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Re: spark plug query
« Reply #2 on: 24.07. 2013 21:47 »
Colin, being in the trade, I keep every plug I remove from servicing. gives me a good variety. but days like this pee me off.
now got a used standard plug in and starting again. prefer Champion but unfortunately we get a better deal and more choice with NGK. ironically with BMW's Bosch are the plug of choice and NGK are a dearer option!

still trying to find if its  plug, cap or what
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Offline muskrat

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Re: spark plug query
« Reply #3 on: 25.07. 2013 10:16 »
G'day chaz. Is the Boyer digital or anolog? Digital needs resisted caps and anolog un-resisted. Are both caps the same? Swap them over and see if the problem swaps too.
Cheers
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Offline chaz

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Re: spark plug query
« Reply #4 on: 25.07. 2013 12:11 »
thanks Musky, will check tonight
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Online BSA_54A10

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Re: spark plug query
« Reply #5 on: 05.08. 2013 11:19 »
The old doge with a fouled plug was to run the engine then slowly lift the bad lead off the plug.
What this does is forces the charge to accumulate at the air gap between the wire & the plug so when it finally jumps the gap the voltage will be high enough to jump the gap in the spark plug regardless of weather the plug has crud on it shorting it out or not.
The voltage to the plug does not slam down the wire at its full potential but rather it builds up to full voltage and as soon as it is high enough it jumps the gap in the plug.
When the plug is dirty the electricity does not build up enough to jump the plug because it leaks down the sides straight away.
In most ignition systems the spark will start to jump across the plug at around 1/3 the rated out put of the device.
The spark continues to occur till the potential is about 1/5th ( it takes less energy to maintain a spark than it does to start one )
We see this as a big fat ( long ) blue spark.

Modern fuels ( which are not petrol ) are very conductive at combustion pressures so if your plug misses a few times and is not hot enouigh to prevent fuel coating the electrodes then the pug will go short ( commonly called bad ) which is what I am guessing has happened to youir bike.
Oft this will happen when you back off and the spark gets a little out of sync with the engine.
I have this problem regularly with the M20 if I do not retard the spark when going down big hills or back off coming into a big sweeping curve
Bike Beesa
Trevor