Have you checked the fasteners associated with the air path (carb, manifold, etc.)? I'm thinking air leak. Head gasket too. Check compression. Check compression release if so equipped.

I think your main jet is cloged in the carb.

The "column" where the bowl nut screws into has passages/
jets that are likely clogged, remove the carb and clean
totally.

Fish

I Googled 12H802 and found your post.

I have a B&S 12H802 in a Toro push mower and have the same problem. The mower is 6-years old.

After sitting in the garage December and January (the only two months I donÂt mow) my mower started up and ran fine at the end of Feb.

I didnÂt use it again until mid March and thatÂs when it would die after initial start. I thought it was the fuel so I replaced it with fresh. Like you, I could only get it to stay running by pumping the primer bulb.

But hereÂs the difference  it started running after a few minutes of repeated priming. It ran rough but then smoothed out and ran normally. It also started right up after stopping to empty the grass catcher at least five times. So I thought it was bad fuel and the problem was solved.

But yesterday, the problem came back. I did the all the checks including air leaks and every thing checked out - although I didnÂt find a fuel filter on the Toro. (manual says "if equipped")

So, IÂm taking advice from Fish and will clean the carb this weekend.

Dan

I wonder if the problem is a leak in the primer bulb itself? I had that be-devil me for a mowing season with one of my Toros. Easy to fix, a new bulb is under 5$ for most mowers

I'm up and running. Check this out. . .

Here is a link that might be useful: Float bowl nut is the jet . .

I have several Briggs & Stratton engines: 3.5HP, 6HP, and two 8HP. If the engine runs for a short period, then you obviously have spark. The only other option is that the fuel is not coming into the carb on a consistent basis.

Rebuild the carb. I have done this on each of my Briggs that were left over the winter with some fuel in the carb and tank. That causes a little buildup of a varnish like fuel in the carb which blocks the jet. You can get a carb kit for about $10-$15 on ebay. Check your engine model number and go to www.briggsandstratton to get download a PDF file of your engine operators manual or a Engine Parts List breakdown.

For your information, my carb kit number is 692703. This link has helped me greatly get all my briggs engines running like they were new.

Mine did the exact same thing!! The first time was a clogged float bowl. The second time it was poor gas quality! I emptied the gas from my mower and got fresh gas, added gas treatment that I bought from the hardware store (Home Depot) for lawnmower engines and now it runs like a champ. I originally changed the spark plug and air filter but, still had the same resaults.

Check the valve clearence,mine would start on a cold start and then die ,the valve stems had to be ground down a bit and then she ran fine....also found some water in the carb ....but the valve clearance was the big issue,once repaired she has started fine ever since....Good Luck Jim

Ok guys you all have alot of very usefull information however i have done everything i can find on every website i can find and all i figured out is that i have the same problem and nothing is wrong with it....

primer bulb is good.. carburetor is 100% perfectly clean.. spark plug is brand new.. fuel is brand new.. air filter is brand new.. already checked for air leaks and none.. already tried blowing in the gas tank.. there is NO diapram in this mower. and many many many other ideas... yet not one of them worked. the only thing that will keep this mower running is the constant pressing the primer bubble... i have completely torn this motor appart and put it back together and there isnt even so much as a scratch inside of it. yet for some reason it will not pull gas on its own...

i have a troy bilt push mower less than 1 year old. briggs and stratton motor 6.5hp 190cc 21" blade

ps i swear to god if someone else tells me to clean the carb again i will throw this lawn mower off an overpass

HAD SAME PROBLEM, CLEANED PORTS UNDER FLOAT WITH COMPRESSED AIR AND SPRAY CARB CLEANER, FIRED RIGHT UP(HAVE TO CLEAN IT GOOD)

Wow. I read another similar blog, removed the screw at the bottom of the carburetor bowl, used a push pin to clean out the small center orifice, and the mower started right up and running fine. I used engine cleaner earlier this year, and probably some debris came loose and plugged this tiny orifice. You could tear the whole engine apart and replace all kinds of parts and never find this simple fix. A new carb would also fix it, of course, $35 at Sears.

POSTOSIS.......DID YOU EVER FIND A FIX FOR THIS Id LIKE TO KNOW WHAT IT WAS..THANKS

ERIC RUBASH
NASHVILLE. TN

I did 3 things and one of them fixed the gas starving gas flow issue. I put a seal lub on the bowl o ring and also on the air intake(with prime bulb) gasket. It appears the air intake unit may be starting to warp and it was not making a good seal to the prime bulb port on the gasket. Also I cleaned the main jet(bowl nut) with a pin but didn't see any blockage.

I have had problems 2 times with my B&S 6.5 Hp.
The first time was a clogged fuel line. I did not start my mower for a while, and the gas in the line turned into tar! I have never seen anything like it. Check fuel lines.

The second time, I cleaned the heck out of my carb, BUT, I did not notice that the brass bolt that holds the bottom of the bowl on has a hole in the top, and 1 hole on each side. Apparently these need to be clean in order for the carb to work. I cleaned them out with a guitar string and some carb clearer, and she fired right up!
Lessons learned. Old gas is bad. Never use old gas, and completely drain fuel from the system before storage.
Another lesson. Find an Illustrated Parts Diagram of your Carb online, and identify all jets (you may be overlooking 1).

I have encountered a similiar problem in the past with my push mowers. One of the solutions I found was to remove the gas tank and make certain the gas will flow through the small filter screen that is inside the tank. Twice after cleaning and drying them thoroughly I had a restriction in that screen from residue. If it is clear, I would next suggest checking the carb needle,seat and float valve to see if it is sticking, clogged or not adjusted properly. Hope this helps.