BALANCER CHAIN LENGTH SPEC:
It should be replaced when the 20 link/21 pin length reaches 193.4 mm: New 20 link length is 190.5mm From 2008 KLR
The balancer chain seems to almost never wear out. Most likely because it is running in a bath of oil. On my 2008 KLR at 97,000 miles length =191mm, almost the same as new.
The loss of adjustment range comes from compression of the rubber shoulders on the sprockets. The chain links ride on those shoulders and as the rubber gets compressed over time, the effective diameter of the sprockets get smaller and the chain gets looser.
On my 2008 I rotated the chain by one tooth in the same direction on all the sprockets including the crankshaft sprocket so there was no change in the balancer timing and gained 1/2" of adjustment range on the doohickey. This is because the inside links now run on uncompressed rubber where the outside links ran before and vice versa.
You can also replace a sprocket to get new rubber and gain adjustment range. The doohickey sprocket is the cheapest and easiest.