Our son's in-laws gave them a Craftsman powered lawnmower, B & S Gold Series 6.5 HP, big rear wheels, front powered mower, it wouldn't start after sitting in the in-law's garage for awhile. It looks like it was used a handful of times by the in-laws and left alone.
He'd tried disassembling the carb for a cleaning, but it still wouldn't run. He asked me to look at it, I said, "ask your 5 yr. old son to help," and told him to bring it over. After a day in the swimming pool (this is Florida) and lunch, we changed and went to the garage.
I stripped-down the carb and found the usual deposits in the float bowl, but no water. Also, when I put a bit of gas in the dry tank, it started peeing-out constantly, a stuck float, probably due to grit or gum.
Removing the float & float valve, I found the main jet totally-plugged with gum and used spray solvent and a fine drill bit to poke-out the deposits until shiny-clean. I used my compressor to blow out the gas supply passage in the carb body, and to ensure the make-up air passage wasn't gummed-shut. The gas venturi from the main jet was clean to the carb main passage.
It was nearly a 'no parts needed' repair other than it could use a new air filter, the old one was dirty-enough to see on the outside it was dirty, though the inside was still clean. The gasket from the air cleaner body to the carb flange needed to be replaced. I had swapped-in a used spark plug to see if it would spark, and when it did, I decided to try using that one, so in it went.
My grandson I showed how to use a ratcheting wrench and socket, and he already knows "righty-tighty, lefty-loosie," to-which he will usually remark, "righty-tighty, lefty-Lucy, Charlie Brown!" He first did that to me when I was showing him screws and nuts, and screwdriver tips when he was age four. I was wearing a 'Peanuts' t-shirt with Charlie and Lucy on it, and he made the joke when I quizzed him about, "now, which-way do you turn the screwdriver?" Man, I was astonished, and 'bout bust a gut, laughing.
Back to the lawnmower. All-assembled, out of the garage, one pull on the starter and it coughs, the second, it catches and quits, the third, and it starts-up and runs smoothly, a bit of smoke out the exhaust for several seconds, and that subsides, and it settles to a good speed. Success. Our son took it for a quick spin in the yard, all is good, and he's a happy camper. He was about to go buy an electric mower for his 1/3 acre urban plot, and fire the lawn service, now he doesn't have to spend anything but tune up parts: an air filter gasket, air filter, and a spark plug.
For being a good kid, helping with the parts cleaning, and tear-down/re-assembly, I gave my grandson a 4-in-1 screwdriver. He already knows the names of the interchangeable tips. Once I showed him how to safely remove and replace the bits, he ran-to his grandmother and showed her how to disassemble it, and how to put it together (grandma is an engineer who just retired after a 41 year career with the same employer).
A fun day in the garage, and the swimming pool.
. But I picked up a 1977 Argosy by Airstream that I hoped would only need a water line repair under the sink. I purchase it with a hope for the best plan for the worst attitude and it's not the best but it's not the worst either. The damaged water line repair, turned into a complete water line replacement, into a remove half of the interior to repair rotted floor. 
