well it started running very sickly, so stripped engine down for good measure - looks like it might have been caused by loose exhaust....
anyway decided to try out my new torque wrench when reassembling, and promptly snapped a stud off in the case... turns out you can't easily get m7 helicoils, not a big problem theres heaps of meat so opened every thing up to accommodate m8 studs... reassemble again with torque wrench and pull threads out of case (probably my inaccurate drilling...) so now everything is heli-coiled m8 and I have assembled by feel rather than by the book, and she runs happily again...
runs happily again now (and I love testing my 2 strokes running up and down Parnell rise (I live near the bottom of it, I don't ride across town just to annoy people))