Clutch arm is HARD to pull

The clutch lever will move possibly 30 degrees or so, but the actual engaging/disengaging of the clutch only takes places within the first 10 degrees or so of the levers travel.

Is your cable well lubricated? If the cable is dry or the cable is binding around the hand lever, this can cause issues of not being able to pull the hand clutch in and it will feel very tight.

using your hand on the lever AT THE ENGINE with no cable is not any indication of how hard your clutch pull will be when assembled correctly.

I've actually had to ride my bike without the cable once. The cable sheathing pulled through the collet that fits into the lever, rendering it useless so I had to use the engage and disengage the clutch by hand. I would push the lever in all the way as it would hold by itself and pedal for a few feet then trip the clutch arm and it would fire up. It was crude but it worked in a pickle. I did not have an operable clutch and had to avoid coming to complete stops altogether also. I had to only make right turns when necessary, or do circles in parking lots to get out into traffic so that the engine would not stop.......it was crazy. It's nice to have a working clutch cable.