Spark Plugs....

[He Man]

How often are spark plugs suppose to be changed in our motorcycles?
Why do we have to change them?

I know we change oil because it gets contaminated with a bunch of stuff during combustion and the friction destroys the lubricating properties of it. However most oils are usually recycled and put to other uses (not sure if they become motorcycle oils again, or just oils for use in power plants only).

But what about spark plugs? Do they stop sparking or something? I know i replaced my plugs on my carbed 900 because they kept on fouling...but on an IE bike, that rarely ever happens. But then why is it that the plug interval between a car and a motorcycle is so drastically different? High RPMs? A v6 and our ducati have practically the same engine RPM range. I swappd out my plugs after 6,000 miles and noticed nothing different (thats all i changed just because i thought there would be something different) and i probably avg around 5-6k RPMs and bump red line atleast once a week form over taking taxis.

Are we suppose to recycle our spark plugs?

[kopfjäger]

http://ducatimonsterforum.org/index.php?topic=12038.0

[He Man]

that thead goes into selecting a plug and how it works, not so much why we replace them.

Assume the plug doesnt foul for 20,000 miles. Then why change it for 20,000 miles? whats the service life of the plug used in our bikes anyway? I didnt see a point in changing them at 6,000 miles (haynes manual says 6200 for 95+ bikes). Im pretty sure if they werent malfunctioning in anyway, i could of just kept them in.

[Howie]

Besides the various deposits, every time a spark plug fires electrode material erodes which means the gap widens and the positive electrode wears from flat to round.  You could file the electrodes and re gap the plugs, but in a repair shop labor is expensive and labor is cheap.  Ducati's interval is probably more often than needed,but a preventive maintenance schedule is just that, preventative, replace before needed.

[hypurone]

Besides the various deposits, every time a spark plug fires electrode material erodes which means the gap widens and the positive electrode wears from flat to round.  You could file the electrodes and re gap the plugs, but in a repair shop labor is expensive and labor is cheap.  Ducati's interval is probably more often than needed,but a preventive maintenance schedule is just that, preventative, replace before needed.

  You just seein if anyone is payin attention....? 

[Howie]

You just seein if anyone is payin attention....? 

Brain fart   Plugs are cheap   Thanks for the catch.

[hypurone]

Brain fart   Plugs are cheap   Thanks for the catch.

Thank you! It made my brain say WTF and wake up this early in the AM! 

[Slide Panda]

What?  You can't translate Howie yet? made perfect sense to me.

Basically, plugs have a crap life - they are blown up and stuck by lightening a few thousand times a minute.  As Howie pointed out, all that slowly blasts the shit out of the electrodes