Heidi, I am thinking it could be one of two things; you need to push back in a bar in the back that disengages the transmission, or, and more likely, you may not have gotten the pin or key back in when when you fixed the flat tire. Did you see a little pin that slides in along the axle? This video may help: https://www.youtube.com/watch?v=YC4LnrfE...

Some engines will have an oil drain plug located on the bottom that looks like this: But, some oil drain plugs will be covered by the housing, in which case, even the manufacturer says you can tip the engine over and drain it out of the fill tube.

Hmmmm, where to start? Make sure your battery is well charged. If that doesn't do it, suspect a bad starter solenoid. To test a starter solenoid, connect a test light to its output terminal then see if it has current. If the light comes on, that tells you this IS power going to the solenoid. If the light does NOT come on, check your battery! Once you know you definitely have power, see if that power is being transferred properly by switching the red lead to the solenoid’s lower terminal. Here is a video. Hope that helps! https://www.youtube.com/watch?v=MsvJMnpQ...

Make sure you got that disengagement bar pushed all the way back in place.

My experience has been that it WILL start and run, but a cracked gas cap will decrease engine performance, fuel leakage, and cause poor gas mileage. Sometimes you will hear uneven engine noise as it surges and slightly dies back.

First make sure you don't have a newer Craftsman with a reverse operation switch that allows you to mow in reverse. This may be simply putting the key in the switch in the ROS position. Or try watching this video. But for heaven's sake, if you do this, be very careful what you back over! https://www.youtube.com/watch?v=6vtakR_D...-I

Potential reasons: * Has your battery got full charge? A weak charge can keep the blades from engaging. * Is your belt stretched too tight, worn-out or damaged? That can cause the belt to snap out of position. * Is your drive belt which is under the seat, okay . . . because it engages and disengages the mower blade. * Is your clutch working? Your riding mower blades won’t engage if the clutches are broken or the cable is damaged. * Is your deck belt damaged? This can freeze the pulley system.

Make certain your oil level is not too high (over-filled). But sometimes, if the mower sat slightly downhill over the winter, oil can pool in the cylinder and wind up in the muffler. This will usually burn off. Sometimes it is a carb issue. Your mower may require a carb cleaning.

According to CoiF on LawnWorld, "Safety switches are located on the Brake Pedal (must be fully depressed); Seat (must be occupied), Deck/Blade/PTO (blades must not be engaged), Transmission (prevents operation when blades engaged and trans in reverse). Since you just worked on the deck belt, I'd look to the Deck/Blade safety switch first. You may have changed the position of the switch or disconnected the molex connector or damaged the wiring. The switch will be located near the "arm" that is moved by the blade engagement cable to tension the blade belt for engagement. When moved to the blades engaged position, the plunger/button on the switch is fully depressed. When Blades are disengaged, that arm moves away, and allows the plunger/button to extend back out. The plunger may be stuck. The connector may have become loosened or dislodged. The wire may have been damaged/crimped/severed."

Try this; when you put the lever on to engage the blade, DO IT SLOWLY and not in heavy grass. Personally, I think the belt is too loose, but you can still often get by . . . if you ease her on.