Tried reversing the collets today without success, googled some more and found advice on "snapping" the closing rocker onto the shim beds the collets in. Tried this and there was noticeable movement of the shim .... refitted cam and clearance resumed ! Some subsequent tweaking of the collets and horizontal cylinder all gaps now in tolerance. Onto the vertical tomorrow Many thanks
Update on progress and my experiences of the Desmo valve service .... This video was a great source of info ..very clear and easy to watch. From my experience, I'd add/note the following for anyone having a go .... Take care prior to removing the belts, marking them clearly to transfer to new belts ... Take pictures so you can look back and verify position (saved my skin ). I made my own closing shim measuring tool as the ebay one was rubbish ... just used a cut down allen headed bolt which slotted neatly into the shim and Vernier to measure. Use a paperclip or similar to hold any loose valves in position on the vertical cylinder when you move to the horizontal cylinder to prevent the valve dropping. I used a small block of wood to wedge the closer rocker arms apart to free a hand when trying to remove/replace the tricky little collets, also a piece of card cut around the valve stem to catch the collet and some plastic tubes stuck in the oil ways to ensure anything dropped was retrievable. Make a table of all the clearances and the shim measurements you remove ... I was able to swap some shims around to save buying new I had trouble "seating" the collets .. you need to let the closing rocker snap the closing shim to seat it securely on that valve stem at least a couple of times - make sure it's aligned first. I went on to cover all the 15000 mile service items and guess it took around 14hrs spread over a week Overall .... time consuming, but nothing too challenging and very satisfying ... total cost in parts just over £200 for the belts, shims (I needed 4) oil, filters, brake fluid, rear brake pads and coolant.
