How to adjust the clutch lever, so first engages

What do you mean when you say you fixed the cable. It sounds like the cable broke and you replaced it. Is that correct. If so, did you adjust the free play in the clutch pedal to the manufacturers specification. If you have not done this correctly the clutch will either not disengage, or no engage properly. From your description it appears as though there is n free play and hence the clutch is staying disengaged even when you release the clutch pedal. If this is the case, then try lengthening the cable until the clutch pedal moves with say 25 mm of free movement before anything happens, and try again.

When engaging the pto it is important that you have the clutch disengaged so that the pto gear is not spinning in the box.before it engages.
The pto gear runs off the counter shaft of the gear box and is spinning all the time the engine is running
when engaging the pto ,you are physically engaging a gear ( like selecting 1st gear) so you have to stop the counter shaft spinning so that the pto gear will engage with slashing

Assuming you've probably got a hydraulic clutch, I'd recommend bleeding the system first to make sure there's no air causing it to not release all the way. If it's the other way around (i.e. it disengages too quickly while squeezing the lever -- make sure it's not worn out -- an overly-thin clutch disk could cause that symptom). As a last resort, if everything's working properly and you're still not happy, try a set of adjustable levers!

Sounds like your clutch is partially engaged.
You may be able to adjust the screw near the lever to tighten the cable (take out the slack) and allow the clutch to disengage when you pull the lever.
If that does't work, the clutch plates may be dry or seized?

follow this steps and fix it. God bless you

Clutch

If the chainsaw chain does not engage the clutch assembly might be worn out. The clutch is similar to an automotive clutch. The chain sprocket is attached to the clutch drum and there are clutch pads underneath. As the pads wear out the clutch assembly no longer engages with the motor and the chain does not engage either.

Clutch Band kit

Chainsaws are equipped with a clutch band, a steel band that wraps around the clutch drum and is activated by the emergency stop lever. If the lever does not disengage the chain does not engage. Check to be sure the stop lever is disengaged. Adjust the clutch band if necessary.
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Drum Brake

Chainsaws are equipped with a clutch band drum brake, a steel band that wraps around the clutch drum and is activated by the emergency stop lever. If the lever does not disengage the chain does not engage. Check to be sure the stop lever is disengaged. If necessary, adjust the clutch band drum brake.

I would say the slave cylinder is going bad.

Pulling the lever releases the clutch. Disengageing it so you don't go. Ok, in order to engage the clutch fully, you release the lever and you must have at leas 1/4 inch free play.
If it is not going in gear easily, you probably have too much free play and you are not fully disengageing.. There is the possibility of an internal adjust ment Try the above and let me know how or if that works. Clutch lever pulled by closing your fist releases the clutch for shifting.

Bleed your slave cylinder on the sprocket cover and refill the hydraulic fluid. If you have any leaks you will get air in the system and it will not fully disengage the clutch. As for the 750, they have cable clutches and you just need to adjust the slack of the cable.

Are you sure it's the clutch, not a seized brake or something? Seems like it would be really tough to push at all if it's in gear (for any distance, anyway). Possibly to the point of dragging the rear wheel. I've got a 74 CB360, and a new battery is probably a good bet (or just charging the old one if it will hold a charge). The charging system is pretty weak, especially if you run with the headlight on. Best to start with a good charge. After that, you can adjust the clutch cable free play at the handlebar if it's just not pulling enough to disengage. Having the neutral light back will give you some indication of shifting success (as will running the bike and feeling it, probably). My guess is it ain't the clutch, but a dragging brake, which is also easy to adjust, but hey, what do I know? And by the way, good choice in bikes. A mid-70's Honda will teach you more than auto-shop would have anyway. PS- In the interest of science, I just went outside and tried to push the bike in gear. Couldn't do it. I think it's not the clutch.