[fred888]

The bike suffered a snapped crank due to failing main bearings - at 70+mph!! - on a left hander!!!
Thankfully both heads and barrels were untouched as the crank went south.
I think the grub screw method sounds good but as I don't trust myself with this level of job, I'll have to save my pennies and get a pro to do it.
Pity the 'pros' that rebuilt the engine didn't realise that shimming out the cylinders would expose the oilway. (they've gone bust since so there's no-one to complain to).

Thanks for the input guys!

Fred