Hi Folks, I am new to the forum so a big hello to everyone here! I've had my Craftsman Riding mower for about 5yrs now, it's a 917.273800 Older Model. I've had no issues with her the past 5yrs, I faithfully change the oil, filter, etc...just about every season. Anyways I fired her up last weekend and seemed to run fine, however when I engaged the blades it was very slow to kick in and I could tell the engine sounded very weak almost like it was losing power when the blades were engaged. Now the only thing I had done prior to this that might explain all of this was treat the fuel with Sta-Bil Ethanol Treatment. Could this be the cause? Or is there something bigger looming. I again mowed the lawn this past weekend and same result, I also on both occasions have heard slight backfires periodically when mowing the lawn. They aren't loud or great but you can hear them subtly. Thanks so much for your time and help in advance!