Joe, I have no idea what does this. I have a 750 here, it runs beautifully until you put a cam in, then it runs in reverse. The problems may be similar or related.
You just know it was the last thing I tested after oiling, disassembling and cleaning, and everything. Ugh. Another clean and oiled parts machine unless I figure it out. In the meantime, I took its throat plate pins as punishment.