loose starter chain on kz400

picked up 75 kz4 that was "halfway" through a restoration job. Previous guy had put on Mikunis, new points, and replaced the starter. Said he got it off another 75 kz400. It works, but the chain is very loose - so much that it bangs on the casing when turning over. I thought somehow the chain had loosened up, or was possibly the wrong length of chain - found another used one and tried it, but got the exact same results. The chain is the same on all kz400 and 440 from 75-82, so pretty sure it's the right one. I don't see any place to tighten/adjust/wiggle anything in the starter, or gear, etc.

Any ideas what could be going on here? And how to fix?

Did you check the part numbers on the starter sprocket. I seem to recall someone else having this issue on a Kz400 and it was the starter sprocket was the wrong one. I took this photo for that thread. It's from a 76 500D3 . It has 13 teeth and 31 splines..

I received a starter sprocket with the new chain, and they were identical - 13 teeth, same number of splines..

UPDATE: there is some wiggle room in the starter shaft. Just enough to tighten up the chain.

I took the starter apart to see what I could learn about it, and when I put it back together, it seemed tight. But then once I put in on the bike and gave the starter a spin (without the chain), it went back to being loose. Any ideas what's going on there?

here's video of the starter shaft wiggle.

I can not tell from the video you posted if the movement is just the shaft, which to me would indicate an issue with the the bearings/bushings the shaft run through. Or if the entire stater is moving, in which case I would attempt to shim it tight.

Hey Thanks! the starter itself is rock solid in there, and when I had it removed and separated out, the shaft part was wobbly by itself. When I put the small gears on the spindle and put it back together, it appeared to be tight, but then went wiggly again after installing it and spinning the starter.