My lawn mower will start for a few seconds then dies.

Same problem as others with Craftsman mower w/Tecumseh carburetor starting up but not staying running for a few seconds or sometimes a few minutes. Discounted ignition as problem as it was clearly a fuel issue so tried all usual tricks of checking fuel cap venting / fresh fuel / standard carb rebuilding [float needle and seat] and cleanout all ports /vents / metering screw, etc as recommended by Chris on this forum. Still no joy and now clearly not fuel not reaching carb problem as plenty of fuel in bowl when removed. Finally figured it out. Mower had been sitting for winter after using gas with no stabilizer, but I couldn't find any deteriorated rubber goods until I looked up into jet tube [this is the tube into which the plug holding the fuel bowl on screws into]. About 3/8" inside that tube is a small rubber O-ring which the plug seals against when tight. It has to form a seal to keep pulling fuel through the tiny holes in the plug up into the jet tube and into the body of the carburetor. When mower has been running for a bit, too much air gets sucked in and stops fuel from being pulled up into carburetor. I changed out the tiny O-ring and problem solved. It is really difficult to get the remains of the deteriorated O-ring out. I ended up using a tiny jeweler's screwdriver and digging it out in pieces making sure none of the pieces plugged up anything else. Just makes me realize how important it is to use gas without alcohol (even if expensive) or some type of stabilizer to prevent the alcohol from damaging rubber goods.

I wouldnt say it has to necessarily be a carburetor problem. I bought a brand new carb, and it didn't change at all. Now it is starting to look like I need to somehow keepnit running long enough for it to start "siphoning" the fuel from the tank and into the carb. Much like siphoning gas from a car's gas tank, the air has to be sucked out of the fuel lines until there is a steady stream of fuel running out, and causing the fuel to continuous draw from the gas tank and into the carb on its own. In my case, I will need to keep spraying starting fluid into the carb to keep it running long enough to maintain a continuous draw.

rebuilding is the right thing to do,but if you can start the machine put a little fuel injecter cleaner in the gas tank. start engine a few times and let sit over night. works 9 out of 10 times

I have often had this exact symptom on an old beast of a mower. It was also a Tecumseh, but not sure the engine brand really matters. In my case, it was water in the fuel which settled to the bottom of the carburetor float bowl. I could do a quick fix by just loosening the nut fitting on the bottom of the bowl enough to let the water and then some gas drain out. Water is heavier than gas so it sinks below the gas. Usually that was enough to solve the problem. A better fix is to remove the carb and clean it, and make sure that the tank is as clean as you can get it too.

Yes, fuel with alcohol is a problem, probably explains why I had this problem once or twice a year.

Our local mower repair shop will do a quick turn-around on carb cleaning / rebuild if I bring in the carb removed from the mower. In busy season, I get the carb back the next day. If they're slow, I can pick it up in the afternoon. Maybe that's just because they like me, it's certainly not because I'm a big spender! They replace the needle and gaskets, and use an ultrasound device to clean out the carb internal plumbing.

That said, there's a spring on the carb on my machine that I once managed to attach incorrectly, which causes the very same problem. I can't describe the spring, but a good repair shop will show you how to connect the springs and linkages on your machine.

I'll bet you have one or the other of these issues.

It sounds like we don’t know . I had this problem with my Honda HR194 mower and gave it to a mechanic who fixed it but the fix lasted only one season. Previously it had no problem for 25 years. So do I buy a new carburettor for about $12 or give it to a mechanic to fix for $50. I tried starting it today (28th Feb) and it started and ran for about 5 seconds. I have to wait about 10 minutes to get it to start and it does so for only 1 second and it continues to work if I spray propane gas into the filter box. My interpretation is that after 10 minutes enough petrol has got its way into the carb but the flow is very slow. Maybe a new carburettor would do the trick.

NGK spark plugs rod in the middle separate when heated after about 15 seconds. Replace plug.

Carburetor bowl.

Memory is the first to go: this happened several years back, but I forgot about it. I had to come to this forum to jog my memory. My bowl has two bolts, one on the bottom and one at an angle. I just took out the bottom bolt, let a few tablespoons dribble out, put the bolt back in, and it cranked right up and mowed the whole lawn.

1 1/2 minute fix after messing with for an hour to no avail.

I replaced carburetor in my Honda lawn mower engine with new one, but it was still stalling after about 10-15 seconds. I replaced spark plug , that fixed it, my old one was pretty bad, burnt at the tip.