Sunday when I was cleaning my wife's grandmas barn and found a Montgomery Ward TMO 33886B 36" Deck mower with 5 speeds and electric start. She said it was junk so I took it off her hands, last night after work I drained all the old fuel and oil for new fuel and oil and a new cj8 plug, removing the air filter and taking out the old battery and temporarily putting in one from one of the newer mowers we have I had it running long enough to do 3 accidental wheelies and ride about 1 minute then it stops. I wasn't surprised that it didn't run great or it probably never would have been in the back of the barn. My question(s) is what do I check / try to fix now since I really haven't done anything but fluids and a plug. I checked the fuel line to the carb. and fuel does leak out I haven't tried anything else since it was already 9pm I checked the plug and it looked good so I put it back in and started it up one last time and noticed that if I feather the throttle by hand along with the choke plate I can make it run wide open or even get it down to low idle but when I use the lever on the mower and adjust that way the motor tries to keep itself adjusted and quits after about 45 seconds. Motor is a 10 hp briggs 220707 0640-01 any ideas on the first thing to check? My background is computers that's how I pay the bills. I can change my own oil, rotate tires, and replace a belt so I'm not handicapped just never had to do any motor work and this seems like some kind of fun in a twisted you off way lol. I would like to get into mower racing this just seems like the first step to get to know mower components and motors better since I will be my own pit crew. Also my wife does not approve.  I have pictures if needed or wanted also if this is posted in the wrong section be forgiving it's my first post.