leaking tachometer cable KZ305

I have oil leaking out of the top end of the tachometer cable, where it attaches to the tachometer. I went for a two hour ride this morning and noticed oil on my pants and upper right of the gas tank. it was also very oily under the tachometer, between the upper and lower fork tube clamps. I cleaned things up with brake cleaner and went out for a 10 minute ride and can see the leak is coming from the cable. I'm surprised the oil can climb up to the tachometer.
Should the cable be sealed in some way to prevent oil from getting in it.

The inner cable is like threads on a bolt.. screws it right up there. It enters where the housing connects to the Cyl. head. Needs a new seal there.

So I assume your saying no oil should be able to get through tachometer fitting on the head cover. Even if there was no cable attached.
That explains a lot. When I first got the bike, it was leaking badly around where the cable attaches to the fitting on the head cover. I put an o-ring in there to seal the cable to the fitting, but that must have just moved the leak through the cable and up to the tachometer. Glad it didn't flood the tech.

As you say no oil should be coming out of there, even with the tach cable off.

The seal for an 81 KZ305 is part no. 92050075 (superseded by920491315). Number 92049 in this diagram: www.cmsnl.com/kawasaki-kz305a1-csr-1981-...47.html#.XtvSi25uLic

You may also want to check the o-ring on the outside of the gear bushing (number 92055A).