Lawn boy starts and instuntly shuts doun

just get started, one step at a time . inspect what needs tobe removed to get to that carb good luck.

yes the key can spin on a lawn boy

pull carb apart and check float,,sounds like it is stuck shut

Yes you can. The only reason small engines have the primer button/bulb is to get gas to the carburator to make it easier to start it. If your mower starts OK without using the primer bulb you will not harm the mower.

probably a dirty carb. or if this problem is occuring when the engine has been run and is hot and its the new style easy start engine with auto choke ( no primer or choke lever) then the auto choke unit coud be faulty

Is the plug getting wet? if not, try introducing fuel to the intake and attempt to start it again, the interlock on the handle works by killing the ignition fire and applying a brake to the flywheel, this should be a Tecumseh engine, carb troubles are quite prevalent on these, by substituting fuel to the intake you are acting as the fuel supply, if it starts and runs briefly you have confirmed a fuel system issue

Carburator problems,the float is stuck wide open.You'll need it rebuilt by a small engine repair shop.Or you can purchase a new one for between $50 and $75.

check for a faulty wire to the engine kill switch it may be contacting the ground

32 parts gasoline : 1 part oil

Either the spark arresting screen is clogged with carbon, or the carb is out of adjustment on the high speed jet.