Spark plug torque specs

[Faber32]

Hi everyone my engine BF25AA (125 cc) requires 17.2 Nm of torque for the spark plug. But in the NGK website for the cr7e spark plug it says 12 Nm.
Now I'm no maniac about torque specs, but difference is big. It's aluminium, so I'd like to avoid damages. What do you guys think? Follow the service manual or the NGK directions? Or tighten by hand?
Thank you

[CROSSBOLT]

By hand and not real tight! I don't have experience with newton-meters but 7 ft-pounds is more than enough. Should finger turn the plug all the way in with no hang-ups until contact with a new metal gasket/washer. These days, most normal production plugs have a "crushable" metal gasket. Once you feel the plug contact that gasket, use no more than about an eighth of a turn, 45 degrees max. There may be others chime in with a better description  soon. The pont here is most of the common errors is too tight and stripped threads.

[Faber32]

In fact, I'd like to avoid damages, it could lead to a loss of compression or other bad things. I'll follow NGK specs, so 12 Nm is fine I suppose. Thank you

[Stig / Major Tom]

In fact, I'd like to avoid damages, it could lead to a loss of compression or other bad things. I'll follow NGK specs, so 12 Nm is fine I suppose. Thank you

Has your torque wrench been checked for calibration lately?
At these very low settings - it is easy to over-torque something as small as these spark plugs while waiting for the "click"....that doesn't come until too late.

Maybe try the "replacing a spark plug without a torque wrench" instructions provided on-line by NGK?

The illustration on the back of the box of my NGK plugs clearly shows that once the new crush washer has firmly contacted the cylinder head - you tighten it (no more than) 1/2 turn.
This will be different if replacing a used NGK spark plug which has already had its crush washer crushed by previous installation!

Stig

[Faber32]

All you say is right :-) I checked torque wrench with a digital torque adapter, it seems fine. Probably those threads have already been overtorqued in the past by "technicians", so I don't know if they're damaged. Who knows