good idling

At last it idles well. Renewing the dip stick and oil filler seals got me on my way. When taking my foot off the throttle and coasting down one of the many hills here in Cornwall the car would hesitate and judder as if there was slack in drive shafts or something. Opening up the idle screw half a turn solved it and the car will idle perfectly smoothly at a much lower idle speed than before. An American mechanic mentioned on the internet that two little fuel would partially seize the engine on the over run. None of the instructions on the Webber sites made much difference. Get it to judder a bit on trailing throttle down hill then open it half a turn. The extra fuel lubricates the bores he said, and it seems to work.

The extra fuel lubricates the bores he said, and it seems to work.

That would apply to a 2 stroke engine with its petrol/oil fuel mix, but in a 4 stroke engine an over-rich mixture is likely to wash any lubricant off the bores - petrol is not a lubricant

That's what I though but all the snatching is gone, right after opening the idle screw half a turn more than Webcon said to.