Small Engines (Lawn Mowers, etc.): Honda self propeller, rear wheels, warranty period

Question
I got Honda Harmony II self propeller mower (model HRT216K2TDA).  It no longer has enough power to propel itself.  The rear wheels turn, but it does not got enough power to go.  I replaced the belt, but that did not help.  Is there an adjustment on these or does the transmission need repaired or replaced?  What would be the cost for these type of repair?

Answer
These repairs can be real expensive, and you might want to check where you bought it, because Honda does have a very long warranty period.

You can look at a blowup of the components here:

http://www.egelhoff.com/pages/parts/viewbybrand/default.aspx

You might also want to make sure that the spring loaded keys that
drive the wheels are not worn out and just not locking the wheels under a load.