Either the air filter is dirty or the flow is blocked when it is installed. Start by cleaning your air filter.
(see the related link)
sprocket worn out, chain brake on....does chain turn free by hand?
A stihl 064 runs a 5.2 cubic inch or 85 cubic centimeter combustion chamber. With a 52 mm bore and 36 mm stroke. It produces roughly 6.5 horse power.
You are trying to force the chainsaw to perform a bigger job for which it is not designed, or the blade is dull (reason for black marks)
More than likely, the fuel filter is clogged or dirty.
Unlock the chain brake
Take the air filter off and see if it runs without the air filter, if it does your not getting enough air and need to replace your air filter.
if it is blocked with debris such as grass cuttings. For research purposes remove filter and start mower without it. If mower runs successfully, you have the cause of the problem.
Yep. You can run it without the bar and everything. It may leak bar oil though as most pump oil as the motor runs to lube the chain. It may have a tendency to rev higher though so don't squeeze the throttle too much.
i do mine at 40 to 1 runs fine no smoke
they all vary i have a Stihl weed eater that runs 50:1 and i have others that run 32:1 and i have one that runs 16:1 it just depends on the maufacture
Fuel filter.
filtrate