Gutted - xr250 head problem

[Flipatron]

After a 60 miles journey to Chester and back on Tuesday my bike developed a knocking noise. It sounded like a tappet had come out of adjustment but after seeking advice I decided to eliminate a few things.

The first think I checked was the oil from the sump for metal shavings but this was a clean a whistle. The next was the spark plug as I'd recently modified the air filter and ground out the weld on the exhaust, I thought this may have caused it to run lean. The plug turned out to be fine but here's the problem, I've stripped the thread on the head and now have no compression!!!

I've still got to find the cause of the knocking noise but now have a stripped spark plug thread to deal with so the heads got to come off now, bugger.

Does anyone have a solution of is it new head casting time?

[raymo]

The plug turned out to be fine but here's the problem, I've stripped the thread on the head and now have no compression!!!
?

you can get it heli coiled

[Lumiya]

Helicoil is cheap and works realy well. Also in the end it's stronger than the original thread