plug coming loose?

[smorris1]

The other day I went to ride my bike and it wouldnt start and it just kept backfiring. I checked the plug and noticed it was loose. Like I could thread it with my fingers loose. Whats weird is the plug has been in there for months and never came loose. I put a new plug in and rode it for a little and then I went to check to see if it is still coming loose and it seems like it looses its tightness after I ride it. Is this normal?

[scuzz]

got any suspect friends or little brothers?

[smorris1]

haha no. I know the threads are fine cause I can thread it all the way down with me using a socket with my hand. Maybe im just not tightening it enough. Is there a torque spec?

[sprayedgt]

What happens is over time, the heat cycles the plug goes through will make the plug back itself out. You're supposed to tighten it twice when you replace it. The first time when it seats go an additional 3/4 of a turn, loosen it then seat it again. But this time go an additional 1/8th of a turn after it seats. It you're just checking it just go 1/8th of a turn after it seats. You need to crush the gasket on the plug first that's why it needs to be tightened twice. There are no torque specs for the plug that I know of.