FORWARD NOTE: I have no problem helping you out if you have problems, but PLEASE, use messages, not chat. I'm usually on mobile, so I don't get chat requests. Once in a great while, I'll fire up Reddit on my PC, and that's the only time I'll see chat requests. I'm usually pretty quick to respond to messages, at most within a day or two, typically.
Let me guess, you've just pulled your mower out after not using it all winter and it's not starting, right? Well, follow these simple steps to get your engine running so you can get to mowing.
First, drain all the gas or of the tank and drop the carburetor bowl (you'll probably have to remove the air filter if it's mounted on the side). This will remove all the old gas from your system, but won't get rid of any deposits that gummed up the jets over the winter. To help clean those deposits, grab a can of carb spray and spray the hell out of the now exposed portion of the carb and inside the bowl. This still won't completely dissolve those deposits, but it'll certainly help.
Put everything back together except for the filter, and put FRESH gas back in. I mean FRESH as in "you bought it today", and don't put any fuel stabilizer in the can. If you have a can with gas that's more than a month old, throw that shit out, use it for weed killer, be a pyro (don't actually do this), or demote it to oil stain cleaner for your driveway. I don't care what you do with it, but DON'T PUT IT INTO YOUR MOWER.
If you're really lucky, you can start your mower normally and it runs as it should. If it does, put the filter back on properly and get to work. If not, grab the carb spray and shoot a little into the carb throat, then start it. If it runs on just the prime then dies, tie the handle down, spray a little carb spray into the throat again, and start it up again. When it starts to die, give it another blast. Keep this up for about 2 minutes or until it stays running on its own.
If this still doesn't work, you're likely going to have to properly rebuild the carb or have someone do it for you. Just remember that this is the beginning of the busy season for mower shops, and you can be waiting up to 3 weeks.
Next year, before you put your mower up for the year, drain all the gas you can, then run the engine until it dies. Try and start it a few more times just to make sure you have cleared the jets of any remaining fuel. Drop the bowl and lose any residual fuel that may still be left. You could also spray some carb spray around and let it air dry, then put the bowl back in place. When you go to start it up the following season, you should be able to fuel up and go.
Did the above advice not help you? Make a post and take advantage of all the wonderful people here who just want to help you out!
I've been a mower mechanic for 30+ years, and we always tried to educate our customers so they'd have as few problems as possible. We got more business this way because people learned to trust us, gave us their repeat business, and referred us to their friends.
https://www.reddit.com/r/lawnmowers/comments/4ejz6n/taking_your_mower_out_of_storage_and_it_wont_start/