Small Engines (Lawn Mowers, etc.): Craftsman mower wont start, engine tune, carburator

Question
Hi Michael,

Thanks for your response.  I tried exactly what you asked.  I also completely disassembled the carburator as well as the pipe leading to the cylinder.  The carb was very clean already but I blew it out to be sure.  The cylinder has some soot in it but not much really- I'm not sure how much is "normal" but it wasn't completely clogged with gunk or anything.

The spark plus does get spark.  I tried spraying "Quick Start" (basically ether) into the cylinder directly and it didn't make any difference.

So where I'm at now is that when I pull the start cord, there's what I think is perhaps some slightly increased resistance compared to what I'd expect but I'm not getting the major kickback that I've seen some people report.  The engine turns but doesn't even come close to catching or starting.

Any more ideas?  Thanks a lot for your help.

Chris



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Followup To
Question -
Hi.  I have a Craftsman push mower engine model # 143.016000.  I got the mower last fall from an acquaintance who bought it a few years ago and hardly ever used it.  The mower is only a few years old, however since I got it, it doesn't run.  I have managed to get it started a few times last fall but it only ran for a few seconds and then stalled.  I just tried today and it won't start at all.  I'm able to pull on the start cord without too much resistance but I hear a thunk (not too loud but noticable) and the engine won't catch or start at all.

Things I've tried: change oil, replace air filter and spark plug, clean carburator pan.  I've also tried adding some "small engine tune-up" fluid to the gas.  From what I know of mowers (which isn't much I admit) I can't figure out why it won't start!  

In doing some reading on the internet, I'm wondering if it's something to do with the flywheel key but I really don't know much about that at all.

Your help appreciated!
Answer -
Hi Chris,

You will need to determine if the problem is a lack of spark or a lack of fuel flow.  Right after it quits, remove the spark plug, reconnect the wire and lay it against the engine head.  Pull the engine over and watch for spark at the plug's electrode.

If good, then try to start it while squirting fuel or starting fluid into the carb intake.  If it starts and you can keep it running by adding fuel, then the carb most likely has dirt, debris or gummed fuel inside.
You will need to remove the carb, disassemble it, clean all the small internal openings and blow it out with compressed air.   Probe each and every hole with a small wire.   A carb rebuild kit wouldn't hurt either.  

Let me know how you make out.
Michael  

Answer
Hi Chris,

An engine needs only 3 things to run:
Timed, good spark.
A proper mix of air and fuel.
Compression.
If you have these, it should run.  
The clunk the engine made might indicate internal damage.  If all these things check out, I might disassemble the engine.  I don't know what else to say.

Keep me posted on your findings.
Michael