Small Engines (Lawn Mowers, etc.): Extremely high effort to pull cord to start Toro, professional service center, briggs and stratton

Question
Toro SR-210S model #20486 walk behind lawn mover. The tremendous effort required to pull the starting cord of the engine is beyond my wifes capability. I have to position the front of the lawn mower against a wall, place my foot on the back of the deck and pull as hard as I can to start the engine (which does start on the first pull). Sometimes I can't budge the engine on the first attempt. I took it to a professional service center who claim they have absolutely no idea what is causing the high effort and returned it to me two days later unrepaired. If you take the spark plug out (eliminating the compression), the effort goes completely away, which I believe means the recoil mechanism is fine. Any help would be most appreciated.

Answer
Good call removing the spark plug.  Does the oil smell like gasoline?  Is the oil level too full?  With the spark plug removed, pull the string quickly and see if any oil squirts out of the cylinder.

You should have a Briggs and Stratton engine on the mower...correct?

Did you visit Toro's website and download the engine service manual?  Toro provides a good engine service manual.

IF, and only IF, the oil is fine, then start by checking the valve clearances.  DO NOT remove head or valves...just start by checking the valve clearance.

Briggs website also tells you how to check the valves:

http://faqs.custhelp.com/cgi-bin/faqs.cfg/php/enduser/std_adp.php?p_faqid=3441&p...

Also, check Youtube for video's.

TIP:  To check the push rods to make sure they are straight, remove one at a time and mark which end goes inside the engine.  DO NOT mix push rods or the direction they are installed!  You can use a piece of glass and roll the push rod on the glass...if the push rod wobbles or it does not roll evenly across the glass it may be bent.

If you have to check the valve clearance, let me know what you find.
Eric