I was wondering if any of you have ever up graded engines on your ztr. I have a Gravely 144z with a 19 kaw. and it is a little underpowered. I was wanting to go to either a 22 or a 25 hp. I have also heard that there are some small engine warehouses online that sell new motors for good prices and was wondering if anyone knew of any websites that are out there. Thanks for the help.