Most vacuum wiper motors have a tubing nipple that is open to the atmosphere where air is drawn into the housing by manifold vacuum. Attach a piece of tubing to that port and submerge it into a bottle of gas treatment or fuel injector cleaner. As the liquid gets pulled through the motor it cleans and lubricates the flapper that operates the wiper arms. It's simpler and easier than dismantling the vacuum motor, and then the solvent cleans the valve guides as it gets pulled through the manifold and cylinder head.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!