Try spraying a 2 second burst of spray carb cleaner into the carb throat and then see if it will start and run for about 2 seconds before dying.
The symptoms you have described sound like it is not getting sufficient fuel from the carb.
If it wants to run strong (for 2 seconds) on a shot of carb cleaner or a spoonful of gasoline into the carb throat you can eliminate spark or valve timing as the cause.
A stone cold engine requires a very rich (in fuel) induction mixture to start and run.
The sputtering and the backfire would be consistent with a lean mix.
Is the float bowl filling up with gas like it should?

few questions first:

did you hit something with running mower deck that stalled engine?

engine oil level checked OK by removing/cleaning/re-inserting/reading dipstick after engine has sat for 30 minutes?

pls post back with info.

No, I didn't hit anything. In fact, I had just left my side yard and was simply driving across my concrete driveway, crossing over to my front yard. Half way across the driveway I heard a "pop", then the engine died right there in the driveway.
Yes, I changed the engine oil a few weeks ago and the oil level is still full.
This all happened several days ago, so the engine has been setting for several days now.

Okay, I just figured out my problem... I just took off the valve cover on one side of the engine and found that one of the push-rods was broken (with a 2" piece missing), and the other push-rod was completely gone! I think i've found my problem! :)
Now I just need to figure out how to get the broken push-rods out of the crank case without tearing the entire engine apart to do so. Any ideas?

I don't know of anyone who has been able to do that, may as well just tear it down. The push rod that is "completely gone" is in there too.

Walt Conner

Yep, I knew that both the 2" piece of the push-rod, and the entire missing push-rod are both in the crank case. I was just hoping someone might have an easy solution for getting them out without ripping the entire engine apart. Guess that's the only option I have available at this point. :(
Thanks anyway for the assistance!

" secrow" should have started a separate thread. Now back to the original poster,

"asand211" the engine quit running before you overhauled it so I don't think you have found the problem which caused it to quit. I would check the flywheel key.

Walt Conner

Is it possible to pull the pieces out thru the drain hole where the oil is drained from the engine ? Maybe get lucky with a magnetized rod,huh!
The engine very likely has a sheared carter key and has thrown the timing off. This happens often when the blade hits an object like a root, or steel post in the ground . It may run for a day or two but when the carter pin finally breaks off, the engine will misfire.
Also, the valve timing will have to be checked .If improperly set, will cause engine to misfire.Lean gas mixture having too much additive treatment will cause engine to misfire.And last but not least, the gas filter may be almost stopped up and cause a lean gas mixture to go into te carb.
good luck! The ole'man!

Another possibility on getting the pieces of push rod out is to take a magnetized rod and see if the pieces are resting on the camshaft---if so the magnet rod may be small enough to go down inside of the push rod holes and pull the pieces out this way.
Again, good luck!
The ole' man.

I have a Craftsman riding mower with a Briggs and Stratton 17.5 HP engine. Engine backfires through the carb when trying to start. I have replaced carb, cleaned tank, replaced fuel filter, checked valves, push rods, and pulled flywheel to see if the key was sheared. Everything looks good. Any suggestions as to what could be wrong.

Several things may cause this,,,old gas,,, gas that is too lean for some reason like using too much additive--you may have hit the blades against a post or a root or something that caused the pin in engine shaft to be partially sheared causing the timing to become premature and backfire,,,,valves may need resetting,,, and lastly, the fuel filter may be leaning the gas to the carbureator,and needs replacing!!!!
Good luck,
The old man.

Thanks for your input but I figured it out. The nut that holds the rocker arm on had backed off.

i have a briggs and stratton 14 hp twin cylinder engine. when i try to start the engine hot the engine will backfire out the exhaust multiple times before firing. what could cause that and is there any ways to fix it.

Check your fuel filter to make sure you are getting a good flow thru it.
Reset your valve timing to make sure it is correct.
Make sure you are not using old gas or gas that has water in it.
Have you hit a big root or post with the blades while mowing??? if so, you may have nearly sheared the pin on the shaft to the points.
Good luck

I just read this and it sounds to me like it may well be the woodruff key in the fly wheel that sits on the crankshaft has moved a little or even snapped......Some times as you mow and it say hits a bit of wood or comes under heavy load that key can move a little or as i say snap. Then when you try to start it you may get a kick from the starter pulley like a horse kicking you in the arm...I would take the top pulley off and the NUT then look down and see if the KEY is in line with the pulley SLOT. If its slightly off line even 3 or 4 mill of line i would take the flywheel off and renew the key or check it and reseat it....It may be some thing else but if you have tried every thing and it still kicks check that..Its quite common...It just put the timing out a little........................................I have a 6 year old Sears Craftsman lawn tractor with a 24 HP OHV Briggs
& Stratton engine. When I was moving the lawn the other day I heard
a "pop", then the engine died. Now when I try to start it the engine
kicks and backfires, but never comes close to starting. We checked the
fuel and the spark and both are present. I can't help but think if it
died suddenly, and now is backfiring when I try to start it that it must
be something related to the timing. Unfortunately, I don't know
anything about how the timing works on that engine. Is it possible the
timing chain/belt (if it has either) could have jumped a tooth? Any
other suggestions for what this could be, and how we would go about
diagnosing?

Most likely a rocker let go of a push rod. Lots of threads to research or best start one of your own as to not confuse the issue.

Ok I have a Briggs 18 1/2 hp paulan pro started right up mowing the lawn turned it off for only a min now it cranks over won't start but backfires through the carb and exhaust I have made sure I have spark all safety switches are working I did run over a small stick while mowing and checked the shear key it seems intact on the fly wheel I checked compression , spark , and fuel I am getting all of this I also noticed my upper rocker was a little loose I adjusted them according to the manual to me seems like timing at this point . Also when I spray starting fluid in motor I still get backfire and no start . I bypassed or altered the fuel switch in the fuel bowl incase that was an issue . So now I'm lost any ideas would be great is there something in the timing I am missing ? I only see one shear pin is there another ?

Always helpful when posting an engine question to also post the model number. There is more than one 18.5 B&S engine.

Walt Conner

I have the same problem as Daniel Griffin. I have a Troy-Bilt 77T tractor with a B&S 18.5hp 752B0301B2 engine. It was running strong, I turned it off to empty the catch bags and it wouldn't restart. It cranks, the flywheel spins and if I crank too long, I get a backfire. The only sound I hear is the starter motor and the whirring of the flywheel. The engine doesn't sound like it is turning over at all. Checked the spark, cleaned the fuel filter and when I rotate the flywheel by hand, I hear the compression. On another note, I got it used and it has always had a very hard time climbing grades. One section of my lawn has about a 15-18% grade and with a running start, it won't make it up. Is this likely a belt needing tightening or replacing?

"752B0301B2 "

This is not the engine model number. Assuming this is a single cylinder OHV, model number is stamped into the valve cover.

" It cranks, the flywheel spins " "The engine doesn't sound like it is turning over at all" ??

"I hear the compression. "

You should be feeling the compression, not hearing it. Suspect valve problem, I would remove valve cover and see if all is well in there, pushrods,, valves working OK, etc.

Walt Conner