Are you checking the oil level? Both before you start initially and when it won't start hot? A little more description of just what is happening might help. The engine doesn't want to turn over or turns over but won't fire? There is a possibility that the carb float needle is leaking gas into the intake, then into the cylinder and on down into the oil (not good). However, you put on a new carb and it still does not do right. What you hear as dripping MAY be the hot muffler cooling and making cracking noises perhaps from running too hot due to partially sheared flywheel key or lean carb mixture. I think I would be inclinded to check the flywheel key. You should be able to do that by removing the cooling shroud, the flywheel mut or bolt and washer and looking down the keyways to see that the keyway in the flywheel and crankshaft line up. Also, installing an inline gas shut off valve and using it when engine is not running might be a good idea. I can send you a PDF of the Service Manual for that engine if you like. Address below, put in proper format and remind me, model number etc. Walt Conner wconner5 at frontier dot com

That might be true, on the vibration. This engine is 24 years old lol; it's still running strong when I can keep everything firmly connected. I HAVE had issues with the engine mount bolts coming loose and have to tighten them up regularly. Discovered when we inherited the tractor from hubby's grandma that the engine was being held to the frame with only three of four bolts, and those just regular bolts, not the OEM engine bolts, if it makes any difference. Got four OEM B&S engine bolts on eBay, and the lock washer that was supposed to go on one of them, but that one somehow came loose and fell out someplace. So back to a regular bolt in that hole. But I periodically tighten those bolts because they do seem to work loose; there is definitely some vibration going on but don't know if it's related to the PTO or not. No problems engaging or disengaging; no unusual vibration. So probably a good case for the carb bolts working loose; once they loosened (before I discovered the problem with them and the engine mount bolts) maybe they started wearing on the bolt hole threads??? Anyway, back to current problem. The bottom screw on the carb mount still can be tightened I think, but the muffler shield on top of the muffler directly below the carb is in the way making it REALLY difficult to access or pull the bolt; you can barely work a screwdriver in there to turn it and you have to bend the back edge of the shield down to do that. I think I need to use Locktite on both bolts though. I tried re-doing the Locktite on the top bolt and tightening the bottom one, and it held for all of about 5-10 minutes of running. After that I ended up bungee-cording the air cleaner to the engine to hold it against the engine block just to finish mowing, but by the time I was done both bolts were loose again. The carb mounts to the left side of the engine, btw. I can link you to a diagram if you like. (see below) I used the same tube of locktite I had from three years ago (still pretty liquid) but maybe it was no good? It was the removable type of Locktite and I am wondering if I should try something with a little more hold? Would JB Weld be better? I noticed it did grip the bolt in the hole better once it began to set but was afraid to tighten it down too much; just turned it till it felt like it was catching a bit and then let it set. Otherwise the bolt would just spin in the hole. I have gotten some more OEM bolts to try new ones but they are shorter than the bolt I used last; last time I just used an ordinary bolt that was a little longer than the original, and it did the trick, but this time I used the same longer bolt and it let go, after applying Locktite, tightening as best I could, and letting it cure 24 hrs before running. Should I replace the carb mount gasket again too? Seems to be ok but I haven't pulled it; I replaced it last go-around. The mower starts and runs just fine if I can just keep the darn carb on the engine! Here is the link showing the carb and air cleaner assembly for my B&S engine, no. 280707-0411-02. If you look at the carb bottom left, you can see the attachment point (intake??) you can also see the bracket I was referring to (no. 662 in the chart). Just a strip of metal that attaches to the little box with the choke linkage on it. Doesn't really support the carb-to-engine connection; the whole unit including aircleaner and bracket moves, I think. It's screwed down pretty tightly regardless. Carb and aircleaner assembly B & S 280707-0411-02 Thanks for any suggestions or advice!

Did you by any chance have the sheet metal shroud (flywheel cover) removed from the engine while you were running it? If so, you may have overheated a cylinder head enough for an exhaust valve seat to pop out of place (and that could be your backfire).

Obviously, it is "turning over" if it "will run for a couple of seconds". You really mean to say (I think) "It will not start and stay running". Possibility #1: If the engine has not used for a while (sitting in storage) the carburetor jets may have become clogged by the varnish that forms when gasoline is allowed to go stale and evaporate over time. Possibility # 2: The carburetor float valve is stuck to it's valve seat and will not allow fuel to enter the carburetor (also due to varnish). Possibilty # 3: If the carburetor has a "Fuel cutoff solenoid", the solenoid plunger valve has become stuck (varnish) and cannot open to allow fuel to the main jet. Possibility # 4: If the machine uses a fuel pump to move fuel to the carb (used if fuel tank is lower than carb....and that covers a lot of machines), the fuel pump may have gone bad during the storage period. Possibilty # 5: Does the machine have a fuel cutoff valve that you have not opened?