I understand what's happening a bit more clearly now... You're standing and pulling the clutch with two fingers, and because your remaining two are in the way the clutch isn't fully disengaging and is getting hot as a result. This then compounds the problem by making the bite get lower and lower in the travel.

You could try firstly, as I mentioned before, taking out all but 1mm of free play when cold. Second, adjust the bite point so it's in the first quarter of lever travel at the release arm. Also check that the index mark on the release arm when pushed as far forward as it'll go lines up with the index mark on the crankcase cover - if these marks don't align then the biting point will be in the wrong place.

Finally you could try fitting some two-finger short levers (which I use) that I have to say do make clutch control a lot more comfortable when standing.

A lumpy single is very different from a smooth v-twin in terms of power delivery, a lot more revs are required at low speeds to stop a one pot motor from stalling, so is therefore bound to be much harder on the clutch. Fitting a 14T sprocket will help/compensate a lot in this respect.

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