Spark plugs

gazzatriumph

gazzatriumph

Legendary Knight
Hi all,
I am useless with anything mechanical so forgive me if this is a dumb question.
My bike is sorn so every couple of weeks I run it in the garage up to running temperature. I didn't bother putting the garage light on today and noticed I could see the spark on both cylinders not at the top bur underneath where the bottom of the spark plug would sit, when I increased the revs it seemed to disappear, is this normal, cheers
 
Don the Don

Don the Don

Legendary Knight
gazzatriumph said:
Hi all,
I am useless with anything mechanical so forgive me if this is a dumb question.
My bike is sorn so every couple of weeks I run it in the garage up to running temperature. I didn't bother putting the garage light on today and noticed I could see the spark on both cylinders not at the top bur underneath where the bottom of the spark plug would sit, when I increased the revs it seemed to disappear, is this normal, cheers
Click to expand...
"No" it should not really do that, is it damp in the garage?
 
gazzatriumph

gazzatriumph

Legendary Knight
Don the Don said:
"No" it should not really do that, is it damp in the garage?
Click to expand...
The garage isn't damp, I'll take them out give them a clean and see if it still does it. I don't usually run my bikes when sorn I don't think I'll bother again as I believe it causes condensation in the engine and exhaust. I thought my mate said to run them but his bike hadn't been started since June that's why he did his crossed wires.
 
MartytheMartian

MartytheMartian

Legendary Knight
I try and run my bikes regularly when they aren't in use as I tend to think that getting them nice and hot boils off any moisture that may accumulate inside the system and in the oil, makes sure a film of oil is regularly coating all the moving parts and helps keep the battery alive as I don't leave it on a charger. I could be totally wrong in my beliefs but it doesn't seem to do any harm anyway.
 
Scrappy

Scrappy

Legendary Knight
None of my bikes had run since beginning of December, so I started the Bonneville and Guzzi yesterday and allowed them to get up to temperature. The Bonneville to circulate the fuel, so our now crappy fuel wasn't sitting for too long in the carbs, and the Guzzi just cos I love the sound 😁
 
Sarky B’stard

Sarky B’stard

Legendary Knight
Not sure I am following your description exactly but it sounds like an insulation failure if you have a visible external spark. Could be:

crack in the plug ceramic
HT lead insulation
Spark plug boot/suppressor cap

As others have said, cool and damp will exacerbate the problem which will either give a weak spark in the combustion chamber or a complete misfire but can be hard to diagnose in 'wasted spark' systems.

How old is the bike? The insulation can age in 8-10 yrs leaving tiny surface cracks that become come conductive when damp.
 
gazzatriumph

gazzatriumph

Legendary Knight
Sarky B’stard said:
Not sure I am following your description exactly but it sounds like an insulation failure if you have a visible external spark. Could be:

crack in the plug ceramic
HT lead insulation
Spark plug boot/suppressor cap

As others have said, cool and damp will exacerbate the problem which will either give a weak spark in the combustion chamber or a complete misfire but can be hard to diagnose in 'wasted spark' systems.

How old is the bike? The insulation can age in 8-10 yrs leaving tiny surface cracks that become come conductive when damp.
Click to expand...
The bike is a Triumph T120 2016
 
gazzatriumph

gazzatriumph

Legendary Knight
The sparks were at the bottom below the rubber fitting. I've taken the plugs out and they are perfect, I put them back in sprayed a little WD40 in to the caps and it started fine and no sparks, although I didn't run the bike long. The plugs weren't loose. The garage is cold but not damp
 
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MartytheMartian

MartytheMartian

Legendary Knight
Hmm this seems somewhat odd. Surely if there was shorting of the plugs to the cylinder head there would be no spark at the plug gap and therefore no combustion? Is it possible that it's some sort of static effect or something to-do with the 'wasted spark'?
 
Sarky B’stard

Sarky B’stard

Legendary Knight
I suspect you have moist air condensing on the plug insulation and this is carrying the electrical discharge from the HT lead both down the central electrode (& firing the engine) AND down the outside under the cap to Earth out on the engine. The spark plug will quickly get hot, dry the moisture and the sparks will disappear. Rev it and the plug gets hotter, faster.
 
Don the Don

Don the Don

Legendary Knight
There was an old trick where you draw a line with a thick pencil all the way down the spark plug and then replaced it , when turned over you could get the spark to track on the outside seen that done a few times the same with moisture it will aid tracking outside the plug
 
gazzatriumph

gazzatriumph

Legendary Knight
Sarky B’stard said:
I suspect you have moist air condensing on the plug insulation and this is carrying the electrical discharge from the HT lead both down the central electrode (& firing the engine) AND down the outside under the cap to Earth out on the engine. The spark plug will quickly get hot, dry the moisture and the sparks will disappear. Rev it and the plug gets hotter, faster.
Click to expand...
This sounds like the cause, thanks for all the replies
 
Scrappy

Scrappy

Legendary Knight
gazzatriumph said:
The sparks were at the bottom below the rubber fitting. I've taken the plugs out and they are perfect, I put them back in sprayed a little WD40 in to the caps and it started fine and no sparks, although I didn't run the bike long. The plugs weren't loose. The garage is cold but not damp
Click to expand...

I use dehumidifiers in my garage even though it feels dry they still remove moisture and prevent condensation on the bikes.

I have one of these on a side:

And also one of these under each of the bikes:
 
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