I have a Troy Bilt 220 self propelled lawn mower. Is there an adjustment for the self propelling mechanism? It seems each season it gets harder to push. It works OK when I am on the driveway but once it gets into the lawn I seem to be doing all the pushing. Any suggestions? I purchased the mower in 2001.

Sounds Like You Have A Worn Belt, Take Your Model And Serial Number To A "mtd" Dealer, And Order A New Belt.
When Belt Arrives, Remove Spark Plug ,
Remove Belt Guard Housing,
And You Can Cut Off The Old Belt,
Then Place The New Belt Over The Blade One End At A Time, Then To The Drive Wheel Transmission.
Reinstall Belt Guard Housing,
Then Spark Plug And Away You Go.