I recently pulled the starter on my 87 and cleaned all the contacts.  For a short time I had no starting issues, but I  once again have an unresponsive starter.  I turn the ignition, I hear the fuel pump prime, but no starter.  I cycle the key sometimes 2-3, but often much more before the starter kicks in.  I am unsure if the issue is with the starter solenoid, or the positive cable itself.  This bus spent all of its life up until last July in NJ, so I do have a fair bit of corrosion everywhere.  The starter isn't cheap so I hesitate to simply replace it, but it is original to the bus with 200k on the clock.
Best,
Finn Runyon
87 Westy Pook
89 Westy Roo