So, only got 150 miles on the running in on the gt186 post rebore and build and was fine until the next day when it was dead.
Had compression so checked spark, none at the plug, tried all the usual including new plug, cap, lead, even the spare cdi, still no spark.
Thought there was no spark off the green on the stator until I pushed it into the dimly lit shed and voila there was one, but still nothing from the cdis, so new one ordered and guess what......no spark!
So, am in the middle of swapping out the stator from the mugello engine and hope to god it works!!