changed my wife's spark plugs in 2010 xl low. front cylinder came right out, the rear was a bastard to get out. once out i could see the reason, but have no idea what would cause something like that--looks like the threads have been welded together. I guess waiting 2 years to change plugs was too long. any ideas what causes this?

 

I would be inspecting the threads in the head. Looks like they are stripped. Make sure you always put Never-seize on the threads of the plugs.

 

We did tie rod ends on my jeep when I still had it Those were rusted fast to the bar. Ended up having to use a torch to get them out. Like the previous poster said use anti-seize on them next time.

 

Definitely stripped in a couple of places!

 

two dissimialar metals the head is aluminum and the plug is steel they have reaction together <electrolysis> and promote corrosion... said in previous post use antisieze

 

Did you have any trouble putting the new one in?

 

I will be willing to bet the threads are stripped all of the way down. Even if the new plug did screw in, it is probably not grabbing a full thread. That would make it much easier for the combustion gasses to shoot the plug right out of the head. If you ride it, keep your left leg clear of the rear plug.

 

Never ever ever fail to pull your plugs and apply anti-seize at least every spring. If you ride year round, twice a year at least, i pull them at every service, never a problem. Steel and aluminum do not like each other too much, they will corrode, add to that heating up and cooling down.

 

You're going to need a heli-coil and use anti-seize from now on.

 

that does not look good at all. Makes me want to pull my plugs right now.