Still running rich

You have to have the timing where it needs to be FIRST or your wasting your time going
any further.If it was mine i would set the initial timing around 18 -20 at 1000 rpm.Total
timing 34-36 at 3000 rpm.Try another carb if you have a 750 with vac secondaries or 650 dp and see what it does.A 850 dp is a big carb i believe thats what you said was on it.Get the timing right