Rattle

Ok guys thanks for all the help AGAIN it turned out the “death rattle” was the starter clutch come loose   I cleaned the taper up with some wet & dry then washed both internal and external tapers with brake cleaner plus a dab of locktight on the central L/H thread bolt and she runs nice & quiet now. I also cleaned the carbs out again using lacquer thinners instead of cellulose thinners and managed to flush out some more residue. The carburation is now spot on. Time to ride and enjoy. 
I really can’t thank you guys enough for all the help. 

This brings to mind an episode many years ago  when I used to be involved with repairing Husqvarna, Stihl and Sachs/Dolmar chain saws.  One of my colleagues checked and adjusted the contact breaker points on a small Stihl. He had quite a battle to remove the flywheel from the tapered mount on the crankshaft. So, unbeknown to me, he coated the taper on the crankshaft with grease before re-fitting the flywheel. This came to light the day after the owner got his saw back - the flywheel had shifted on the taper, shearing the woodruff key in the process, and of course throwing the ignition timing  out.  When I questioned my co-worker’s decision to grease the taper, his reasoning was that since he’d had difficulty removing the flywheel, he wanted to make it easier ‘the next time.’
I recall reading somewhere that there should not be so much as a fingerprint on the taper, never mind a dollop of grease!