Meltdown!!

After 7 days of vacation in Jylland at the West coast, were we drove alot of miles... The bike did a great job with No problems at All. When we came back to sjelland and headed home, i wanted to test the top speed and efter 10 minutes of full throttle, it suddenly lost power...
I managed to get the bike home running it slowly...

Next day i took out the spark plugs to see some indications of what had happened. Left side plug was melted and i knew there was a hole in the piston.... Damn! As you Can see on the center and Right plugs, ignition and carburation is correct, the reason why the left plug melted is because the previous owner fitted a new Steel thread for the plug wich is made for short plugs, for lawnmovers etc..