Rotary valve worn?
Check this out:
Or, the high speed circuit is still clogged in your carbs. Sometimes, these carbs simply need to be completely replaced to rectify this. Please post your results.
Adjust your oil cable. It's getting too much oil. The hash marks on a 951 are REALLY hard to see. I used a camera. I had the same problem when I went thru my carbs...
Good luck!