Damaged balancer chain sprocket on the crankshaft of my KLR 650 Motorbike.

The damage to the balancer chain sprocket was most likely caused by a loose balancer chain, which was caused by the failure of the balancer chain tensioner system (I found that both the "doohickey" and the tensioner spring were broken, which is a common failure in the KLR 650 engines).

The bad news is that replacing this sprocket (a part that costs less than $40) involves taking the engine off the bike and splitting the case open (i.e. basically taking the entire engine apart). That's a 20 hours job at least.

By comparison, changing a valve is a breather.

Even worse: on the newer KLR 650 models (post '97, i think), this sprocket is integral part of the crankshaft, and it cannot even be ordered as a spare part.

All this work to change a small sprocket! What did the Kawasaki engineers think about when they designed it? it would have been simple to design it so that this sprocket could be replaced easily!