If you have dust sticking around the cam chain tensioner, you might have an oil leak due to a failing gasket on your Suzuki DR650 or your DR-Z400. (they use the same gasket)
 
Also, if you plan on working on the starter motor, you will have to remove the cam chain tensioner, and consequently, it's a good idea to replace this gasket with a fresh one for re-assembly.
 
This is a Suzuki Genuine Parts:
12837-24A10-000 GASKET, TENSIONER ADJUSTER