Max wrote:I suppose it's hard to say, I guess the plug was shorting against the head (or rad)... as an aside I think it is less likely to seize on a full open throttle, but not impossible.
What's the worst that can happen by running it again? If it did seize then the damage is already done, I suppose you can't make it any worse...
The good news is you found a possible culprit!
I’ve got a new set of plugs on order so when they turn up I’ll take it out again and see what happens, hopefully it won’t completely destroy itself if it does let go!