750b starter chain

I've owned my 77 750b2 for about 4yrs now. This whole time I've been starting it using the kicker exclusively. My knee is starting to become an issue and it's now time to sort out the electric start issue on my bike. 

when I bought the bike the seller stated the electric start didn't work due to a missing chain. I'm betting that's only a half truth, I suspect the starter clutch locked up and they removed the chain instead of just repairing the clutch. 

I have verified the starter works with 12v supplied to it directly, so we are good there. But now I'm preparing to remove the dynamo cover and assess the situation and address the starter clutch. 

I'm guessing the bike is missing the chain that connects the starter sprocket to the flywheel. My factory manual gives me slack measurements for the chain but does not list a chain size or link count. 

does anyone know the size chain I will need to order? Trying to have all the parts ordered and on hand before I start disassembly. 

I would be surprised if anything is missing. When a starter clutch goes bad, it will essentially freewheel. 

Not sure if this will be of any help or not. This is a link to info on the starter clutch on the 750 twins. No mention of chain you are seeking info on.
kz750twins.com/?p=37

If you need one there are also parts lists on the same site
kz750twins.com/?p=418

This is the chain you are looking for (listed for 77 B2 on CMNSL) although I would question why it was re moved 

Thanks everyone, now that im home from work I'm fighting with some previously rounded fasteners on the cover, thankfully I have the allen head stainless replacements on hand, once those are off I'll grab some pictures of the situation.

The part seems difficult to find in stock on just a quick search. Hoping someone knows the chain size and I can just make one out of bulk chain. 

Those 750Twins are renowned for starter clutch issues. Often the sprag clutch behind the rotor. As Wookie mentioned, could of been binding-up in the past and dragging the "reduction" starter along for the ride. NOT GOOD.     Honda CB450/500 twin used similar and they used a peanut 219 or 8mm chain. But one in photo of used ebay items looks beefier then a 219? Anyway a nice collection for 25bucks plus shipping?? If it helps. 

The below link relates to a similar situation and the pic is what happens to a starter if it becomes driven by the motor (this one is from a 750 twin !!!)

1982 KZ750 Twin Starter Motor Not Turning Engine - KZRider Forum - KZRider, KZ, Z1 & Z Motorcycle Enthusiast's Forum

  So it looks like you all were right so far, the seller was incorrect about the chain being missing. It's clearly there....

Ive only quickly bumped the starter using jumper cables a few years ago to confirm it would spin, previous owner cut the wiring going to the kill switch and starter button and I haven't touched it yet as all other controls work. Any harm in pulling the plug wires and trying to turn the starter with the dynamo cover removed?    

Probably be kinda messy with oil everywhere and as I understand it there is a chain guide in the cover, can you rotate the starter gear on the rotor by hand (you should only be able to rotate it one way) If you can turn it both ways then you can save yourself a clean-up as the starter clutch will need attention

Thanks that confirmed the starter clutch does not properly engage