Mine pulls hard between 8-10k but at 10k it stalls again. I would be ok with a range of 9-13. But currently it isn't good enough to pull out in traffic.
I found a fuel filter was reversed and corrected that. Much better afterwards but not good enough.
I don't have a spark plug socket so Im going to wait until I can check/replace the spark plug.
I feel kinda stupid. Should have checked the plug first... My other bike is a four stroke and I have to remember the differences.
I will also try raising the needle. Took the bike to a parking lot tonight with some of my friends. One of them brought up raising the needle. I think its certainly worth a shot.