Small Engines (Lawn Mowers, etc.): sick lawnmower, sick lawnmower, float bowl

Question
We have a craftsman mower w/ Tecumhsa engine.We've replaced the pull, spark plug and filter and changed the gas and oil. The mower starts but conks out quickly. Any suggestions?  

Answer
Paula
Most of the time, the possible causes and solutions will be similar to those where the engine doesn't start at all. So, see the following sections for more information. However, here are some specific issues dealing with engines that do start eventually and then run fine:

Cockpit error: If you have a user manual, read it! The starting procedure for all engines is not the same. Make sure you are following the recommended starting procedure. This may not always be best but it is a starting point (no pun....).

Number of priming cycles: The instructions on priming are often optimistic. In colder weather, twice as many presses of the primer may be necessary. However, overpriming and flooding is also possible. Don't overdo it.

Condition of gasoline: Old or contaminated gas will make any engine harder to start. If the problem is with an engine using last year's gas, drain the old gas completely and dry out the residue in the fuel tank if possible. If debris or water is found in the old gas, the carburetor may need to be drained and cleaned as well. Then add fresh gas (not from the batch sitting in the can since last year!). In cold weather, the water can turn to ice inside the carburetor float bowl causing all sorts of problems including flooding of the engine.

First start of the season: If no maintenance was done at the end of the last mowing (or whatever) season, the first time the engine is started may be tough. However, this may be a one-time problem. Hopefully, maybe. :) Even if all the recommended maintenance was done, the first start may not be perfect. And, for float-type carburetors, after filling the fuel tank, wait a minute or so for the gasoline to fill the float bowl before pulling the cord! Think: FAST - Fuel, Air, Spark, Timing. Diagnosing a balky engine is not difficult but a step-by-step methodical procedure will make it a lot less traumatic. Despite all the warnings, serious problems rarely develop on their own. Most likely, there is a simple, easily remedied cause