1969 T120R Primary Chain Wear

Photo at left shows a newly installed primary chain in 2015. The right-hand photo shows the same chain two years and 11,000 miles later.

I change the primary chain case oil (30w Non-Detergent) every 1,000 miles

Still trying to figure out a better way to check the chain tension, but I try to keep the chain not too slack, not too tight.