Small Engines (Lawn Mowers, etc.): Starter issue, fly wheel, battery cables

Question
John, I have an old 1989 MTD lawnmower that I have had to replace the starter on the last two years.  This year I have a new battery, starter, and solenoid. Am I doing something wrong or can something else burn a starter out that perhaps I should replace?  Or, do you think that I had a defective starter.  The company was nice enough to replace my starter, but I don't want a reoccurance.  

Notes on my installation: When I put the starter on (which is a 'replacement' part number (not OEM)), I have to adjust it to make it engage the fly wheel.  If I don't get the bolts just right, the starter engages, but doesn't turn the wheel.  (It comes up just a little outside the wheel.)  Once adjusted, though, it seems to turn the wheel and drop back into case okay.  When I turn the fly wheel by hand, it seems quite tight, but perhaps that is normal.  Hope all this makes since. Thanks very much for your help!

Answer
 Hello Tim:

 The Problem you described could be a Defective Starter. However I would Remove the Spark Plug, Remove the Belts from the Engine Pully.  Turn the Engine BY HAND and see if it Turns Smoothly and Easly. Approx. 10 to 15 ft lbs should Turn the Engine. Less than that is OK. If this is OK then the Starter; 1- was Defective or, 2- The Cables may be Corroded inside the Shield or I have found Replacing the All The Battery Cables (from Batt to Soleniod, Batt to Ground and Soleniod to Starter) with a Larger Diamenter Cable solves this Problem on some Mowers. The Larger the Cable the Better the Amp Flow is to the Starter. 3- Make sure the New Starter is SHIMMED to Proper Gear Depth. The Starter Teeth should ONLY CATCH ABOUT 3/4 OF THE GEAR. If Set too Deep the Starter will Draw too much Amperage and Burn Up the Brushes inside the Starter.

 Good Luck

 Respectfully

 John