Checki your valve clearances, and open them up justa a tad if they are under .006" each. The valves may be a little noisey at .oo6", but it usually helps keep reversion, caused by cam duration to a minimum. The cam induced reversion is usually minimized, with a cv carb, due to the vacuum operated slide.
If you can find a 28mm CV carb, you might want to try it again. CV's usually tune real well with a combo like you have. I ca't imagine why a broken chain agjusted would have affected carb tuning....had to be coincidence. As for the other carb...(CV) I'm at a loss. Unless you developed an air leak some where in the intake tract, by some sort of impact, when the chain adjuster broke.
Just a few things to look at, hope some of it helps.
__________________
kliff
|