247.38908 Mower Won’t Start

21″ Model# 247.38908, B&S 6.75 HP
Will not fire at all. Doesn’t even try. This mower is 3 years old, but has maybe 6 hours use…it’s like new. Things I have tested/tried:
1. New spark plug is sparking well. New air filter.
2. Carb clean and rebuild kit done, but everything looked fine, like new, clean and nothing was plugged. Can see light through the jet.
3. Oil was full,clear, and clean, but I changed it anyway.
4. I tried putting a shot of gas straight into the spark plug hole, then quickly replacing the plug and wire and cranked it. Nothing, not even a little pop of trying to start. A small puff of white mist came out of the exhaust once or twice.
5. I removed the spark plug and placed my thumb tightly over the hole and had someone else pull the crank and felt no suction or compression at all. Not the slightest burp or anything. When cranking it fully assembled it sounds normal though. You get that puff puff, chuh, chuh, sound.

All linkage and cables are clean and move freely. There is nothing to adjust on this one. No needle valve or anything on the carb. It’s just a tube with a single jet sticking up in the middle of it, and going down into the float bowl (which is also working fine, filling with gas).

I would sure appreciate any help with this. Is there something I’m missing? Some pollution control valve that may be stuck or something?


5 answers

  1. I am sorry you are having a problem with the mower. If the Intake valve is hanging open I suspect the stem may be rusty. If the valve was open, when you put it away and was stored in a humid environment for some time, it could have rusted the valve stem. When this happens, the valve could hang up. To cure this problem you can try removing the valve and cleaning it with steel wool and WD-40. Once it is cleaned, reassemble the engine and check the operation.

    I hope this is helpful. Please let me know if you need further assistance.

    1. In response to markexpert

      The mower was never stored for any length of time but was kept in a garage. It was bought and used regularly on a very small yard in Mesa, Arizona (Not humid at all). Thanks for the advice, but it is just not worth putting any more time and money into, with new gaskets and the like to tear it down that far.

      I'll just have to buy a new mower, not Sears/Craftsman/Briggs and Stratton.

  2. I tore the head off and found the problem. The intake valve was stuck wide open. I slipped a screwdriver under it and pried it wider open thinking it was probably broken in half and would come right out. Instead something inside snapped into place (spring was stuck in compressed position?) and it began to function normally.

    I put it back together and fired it up in one pull. Let it run about 5 minutes, everything was working fine. Shut it off. Tried to restart it, and it was dead again.

    Conclusion: It's not worth fixing. What engine can not handle 6-10 hours of very light usage before developing sticking valves in the first place though? This thing was like new still. Had not even gotten the original spark plug dirty. Not happy, at all.

  3. Welcome to MySears! Thanks for the excellent details on your issues, C.Hill! We appreciate you explaining this so thoroughly. This will allow for the Lawn and Garden Experts to diagnose your mower problems the best they can. Check back soon for a reply!

  4. More info: This is the mower or closest thing currently

    When removing the spark plug after cranking it a few times, it is moist and you can smell gas on it. So, it is sparking, it is getting fuel. How on earth is not starting? Not even sputtering or back firing, nothing.