I have a Homelite ST200 String Trimmer. It has always been hard to pull to start. It seems you are always pulling against high compression. Could this be a timming issue?

Hi,
Not necessarily as this machine was made from the Super2 chainsaw powerhead. If you have ever has the rope replaced and the small plastic washer was not used, then the pulley is probably opening up on the side with the knot. This will cause extra drag because that side will have reduced tolerance, or clearance with the flywheel.
Peace,
Clarke