air leak thru the spark plug

[scooter_italiano]

At the end of a 200cc kit rebuild I've found an air leak coming thru the spark plug hole.
Putting grease around the threads of the spark plug seems to improve sealing but the leak is still audible. any suggestions?
grazie!

[nelson pk]

If its an old plug, the sealing washer on the bottom could be crushed beyond sealing if you know what i mean. Try a brand new plug if its an old one.

[Trojan]

The spark plug washer may do for now, but the downside may be the threads are worn in the head due to overtightening worth a look.......

[scooter_italiano]

The spark plug washer may do for now, but the downside may be the threads are worn in the head due to overtightening worth a look.......

that's true but for now it works!
grazie mille!