So what exactly is the "Doohickey"?
The "doohickey" is the KLR650 community's term for the "Balancer Chain Adjuster Lever".
This lever has an adjuster bolt (that goes through it) and when loosened, allows the spring that is attached to the lever to remove the slack in the balancer chain. The stock lever is actually two pieces welded together to make the lever.
The stock levers and springs of the 1987 - 2007 KLR650 have a history of breaking/failing and occasionally causing significant engine damage as the broken pieces get loose. The 2008 KLR650 has a completely new lever, machined from one piece of steel. This is an improved part, but it has been reported as having some play when fitted to the shaft, and that the spring provides very little if any tension at all.
Here are a few photos of what some of the KLRWorld.com Forums members found when replacing their doohickey-
What GreenGene found -
What Gunny found-
In the KLR650 community it is standard practice to replace the stock lever & spring with better replacement parts.
Changing the lever & spring requires 2 special tools- a special bolt used to remove the rotor and a wrench to hold the rotor. Once the rotor is removed, the inner case cover is removed and the lever and spring are easily replaced.