The 660 uses an auto decomp, long story short as the starter turns the motor over there is a pin on the camshaft that decreases combustion chamber pressure by holding open a valve. When the engine starts it rotates at a higher rpm, causing the weights to shift out and retract the pin returning the valves and rocker arms to normal operation.
Being cold/hot does not affect the operation of the decomp, but if your valves are improperly adjusted it could cause you to feel as though it as "too much compression".
I would suggest adjusting the intake and exhaust valve lash to OEM specs (usually in the middle, or slightly tighter than the middle of their spec) and see if that resolves your problems.
