the chain is a 530 type.
Sometimes also called DID50, but that is typically a very simple, old style chain.
Todays there are O-ring, X-ring or even W-ring chains in use.
For our Twins an O- or X-ring would be fine.
Chain must have 106 links.
Rear sprocket has 38 teeth.
Front sprocket has stock 16 teeth, but a lot of guys changed that to 17 teeth.
The front sprocket of a Yamaha SR500 would fit perfectly and is a cheap trick ! 😉
That will still fit with the 106-links-chain.
The final chain link is a special thing !
Often rivet locks (german: Nietschloss) are offered, but they need an expensive special tool to get riveted as they should be.
I don’t use them at all!
Best solution is to buy a chain that is “endless”, means the ends are factory coupled and no lock is needed.
To mount them, the swing arm needs to be taken off the bike.
Rear wheel must be removed at all to replace rear sprocket, so the “heavy” part of swing arm removal is already done 🙂
Removing the swing arm is more work, but allows to check, clean and grease swing arm bearings and axle.
BTW the swing arm and the rear side of the motor and that area of the frame can be cleaned as well.
I bet it is time to do that !
Other kind of lock is a “Clip”-lock. That is old style, has some disadvantages (neglectable with our Twins) and the advantage that no special tool is required to fix / fasten it as it should be.
I typically use a special kind of lock, a “screwed” lock. It is made from ENUMA and I use their matching chains as well.
Patented, expensive (approx 12,- Euros) and superb.
It has two long bolts with a thread. All other parts of the link (o-rings, latch) can be placed in position and the nuts are used to press the latch onto the bolts until it is firmly seated in final position.
When finished, remove the nuts and simply break off the threads. That’s it, done 🙂
OK, here the short summary:
16-38, alternative 17-38 sprockets,
chain 530, O- or X-ring, 106 links,
endless or with matching lock.