"?" about spark plugs

[Guest]

What happens to a spark plug over time that will make the bike harder to start? The plugs look clean, light tan, electrode is not worn. But I have noticed that after putting in new plugs a bike will start faster and easier. Do they build up resistance or something else?

[rphillips]

These days, most everyone uses resistor plugs, except me, I even take the resistors out of the spark plug caps. I've never liked the idea of anything that slows or weakens the path of the spark, no matter how minor. Just thought, if you were using resistor plugs, the resistor may be breaking down & slowing or weaking the spark too much. If you aren't using resistor plugs, I wouldn't have a clue.

[Nessism]

What happens to a spark plug over time that will make the bike harder to start? The plugs look clean, light tan, electrode is not worn. But I have noticed that after putting in new plugs a bike will start faster and easier. Do they build up resistance or something else?

How much time are you talking about?

My understanding is that our old GS bikes don't have a whole lot of spark energy so to speak, so it's not surprising that dirty plugs make the bike harder to start.

[GS1100GLMLA]

Have you checked to make sure the gap is within tolerance? That can make a big difference on our motorcycles. Proper gap makes a big difference in how efficient an engine runs.

[SqDancerLynn1]

Have you checked the voltage going to the coils ?? It could have weak spark. You could have a weak battery too!

[KEITH KRAUSE]

Always helps to have a nice new connection in the system, even if it's only one of many.
Brand new plugs would have the least possible resistance. I think the "metal qualities" of the grounding electrode change with miles. The tip should get slightly annealed and that does create more resistance to electron flow (amperage). Any rounding of the tip, even though normal, will also somewhat compromise the spark size/path.
So combine a thin layer of carbon, and more resistance, and you'll notice a little difference. Add a bigger problem, like incorrect jetting, etc, then you'll notice a bigger initial improvement.
I just recently changed my '79 1000 plugs after more than 20,000 miles. They looked fine to me and the gap was fine. Just a very slight rounding of the ground electrode tip. I couldn't really notice any improvement but I wasn't really focusing on it at start up. I run the Dyna S and green 35K coils.
Only reason I changed the plugs was because it was the bikes birthday and I ALWAYS get it something for it's birthday.

[bwringer]

I just recently changed my '79 1000 plugs after more than 20,000 miles. They looked fine to me and the gap was fine. Just a very slight rounding of the ground electrode tip. I couldn't really notice any improvement but I wasn't really focusing on it at start up. I run the Dyna S and green 35K coils.
Only reason I changed the plugs was because it was the bikes birthday and I ALWAYS get it something for it's birthday.

I was about to post exactly the same thought!

If the rest of the ignition system is working correctly, new plugs will make no difference at all. Neither will colder, hotter, iridium, platinum, or any of the other horse manure plugs you'll find out there.

I stick in a set of the standard (and ideal for my engine) NGK B8-ES plugs once a year out of habit.