LawnMower Man...Mmmm Hmmmm

[Fordum]

Nope, it uses the straight gravity flow carb looks like.

In that case, unless there is a connection from the carb to the crankcase, its got to be a bad float valve.

That is the reason its hard to turn over after you stop it.
The engine is hydro-locked with gas.

Its just like my old 8N Ford tractor. Its got a fuel cutoff on the tank, and the first thing you do when you shut it down is turn off the fuel.

The old carbs on those tractors were notorious about leaking, and with the tank over the motor, it would fill the engine up.

Yours may have a little fuel cutoff on the bottom of the tank. But a carb rebuild or replacement will probably do wonders.

But do it quick before you burn up the engine. If it has the cutoff, use it until you can get the carb fixed.

 

[Fordum]

Sorry for all the false leads, but don't forget Briggs makes thousands of models, and it took me a while to sort through all of them in my head.

You see, I know everything, but the filing system sucks............

 

[Chief Brody]

I just paid $250 to have the "Carburetor rebuilt" at a local Toro dealer...maybe he didn't do his job right?

 

[Fordum]

Sorry, Life intruded.


Sounds to me like he didn't. If you can loosen the intake manifold bolts slightly after it has run for a few minutes, and see if gas leaks out from the gap, that will tell you for sure.

But, while you might get a little contamination from ring blow-by on a worn engine, if enough gas was getting by worn rings with a good carb to hydro-lock the engine and dilute the oil, it would not have enough gas staying in the firing chamber to run.

So, raw gas is going into the engine from somewhere, and since you don't have a pump on that model, unless you see a line going from the tank to the crankcase, then its got to be coming through the carb.

And there's not going to be a line from the tank to the crankcase. The carb is the only connection.

To be honest, I'm surprised its running OK. Unless the system is building up pressure, ( check your gas cap vent ) it should be flooding badly.

The float might be sticking when its stopped and the vibration is keeping it from sticking when its running.

I think 12hp is two cylinder. Not sure off the top of my head. If the plugs are easy to get to, try pulling them after it runs for a while and then sits for a few minutes.
In other words, when it usually doesn't want to crank back up.
Spin the engine over and I bet you will see gas shoot out the plug holes.

In his defense, if he rebuilt it, and it cranked and ran well, he could easily have missed the leakage problem.

 

[79rustyk10]

I wouldnt go back there. Ask around and find a good small engine sales/service place.

 

[Fordum]

BTW, if I am looking at the right engine, the carburetor complete, model number
498027 is $125.
Sounds like he sold you two...............

And, again, if I am looking at the right engine, BRIGGS & STRATTON MODEL NO. 286707-0119-01,
Then the complete replacement is $460 from here:
http://tewarehouse.com/21B907-0029

I have bought one from them before. It was not the recommended model like this one is, but from the specs I thought I could make it work on my pull behind bush hog mower, and did.
The mower did not come with electric start, but I found a motor from them that was and would fit.

 

[lectric80]

Before you spend any more money, pull the float bowl off. For the few minutes it will take to do it, it is peace of mind.

Since I know you will want to know why, last year my Dad picked up a Dixon ZTR 3303 from 2002. Previous owner said it never ran right, and always seemed to be flooding out. Had maybe, maybe, 25 hours on it, but it wouldn't start. Dad brought it to my place to have me take a look. First step, pull the air filter, check for fuel flow. Didn't seem to be getting any fuel, so I pulled the float bowl. Somewhere along the line a simple little pin had been left off the float, causing it to bind and not close the needle. $2 part later and the mower runs like a champ. Unfortunately I have gotten used to running the thing on my yard, and Dad will be taking it away this weekend. Guess I need to get my 13 year old doing some strength training to push the mower around the yard.

It is worth the look at least, you might find a damaged float, no float, or a missing hinge pin. All are easy fixes, and all should be taken out of the guys hide if they are found. It is a simple bolt at the bottom of the bowl, and it will come right off.

 

[Chief Brody]

Thanks, I will have a look..the reason for the $250 was the labor charge of $60/hour...

 

[diesel4me]

250 bucks to rebuild a Briggs carb??...gee,I guess I am not charging enough,I usually am lucky to get 25 bucks to clean a lawnmower carb!....I could have sold you a better tractor for that much...

If you have a cyngle cylinder 12 hp Briggs,it has a flo-jet carb,that are noted for doing this,and sometimes no amount of tinkering and replacing parts like the float and needle & seat valve will stop the carb from leaking gas into the crankcase when the engine is off...I think the carbs crack internally or something.
....when I get one of those carbs that does this,I just buy a new or "good used" one..even when you have a "good" one,you must use a fuel shut off valve and remember to close it when you shut the engine off,or better yet,let it run out of gas after shutting off the fuel...these carbs start a "siphon" once gas starts draining into the crankcase and wont stop till all the gas in in your crankcase,or on the floor of your garage--hope its not stored indoors!

I have seen many newer lawn tractors with 2 cylinder engines blow head gaskets at low hours,and the engine will start smoking like a tire fire,and it can also cause oil dilution,when the head gasket blows,its usually in a area where its very narrow that seals off the crankcase where the push rods go down into the block--that will allow compression to pressurize the crankcase and force oil into the breather and into the carb,where it gets burned..and it'll force gas past the needle & seat and flood the crankcase..

Many people junk an otherwise perfect tractor with low hours when this happens,when all it usually needs is 2 new head gaskets,as long as it wasn't run until it ran dry on oil of course...this is a common problem on many 2 cylinder Briggs and Kohler engines ..

If your engine turns out to be toast ,a good place to find a new one cheap is www.surpluscenter.com --- or www.smalleniginewarehouse.com ..most any vertical shaft engine will bolt up in place of the 12 HP briggs,even most 2 cylinder ones...there may be wiring or other mods needed though to make one work,usually not a big deal...

 

[swedester]

the carb on my 12hp briggs has a small rubber seat for the float needle,wich got swollen(spelling?)and never worked properly,a rebuild kit for the carb fixed that,for about 25$
runs perfect now.
wonder if the rebuild guy put in the wrong needle?there was 3 different ones in my kit.

 

[Indy4x4Fab]

this is so easy can i have a harder problem to fix. ur float needle is stinking open, one the floats bad, two there needle seat is torn or theres simple a very small peice of trash keeping it from sealing up properly. the tank is located higher then the bottum of the bowl so if the tanks full then theres more then enough force to fload the cyclened. now the rest of thr story the cran case breather hooks on to the side of the carb where the carb brace attaches to the carb. simple take the carb off the engine have it rebuilt by a small engine shop and ull be as good as new.

 

[Chief Brody]

I called them...they want me to bring the whole lawn mower back...PITA getting it into the truck...
I am contemplating taking the carb off and taking it to them..

 

[Chief Brody]

this is so easy can i have a harder problem to fix. ur float needle is stinking open, one the floats bad, two there needle seat is torn or theres simple a very small peice of trash keeping it from sealing up properly.

You were absolutely correct....I took it back early this morning and they changed the oil, put in an inline fuel filter, flushed out the entire fuel system, and pullrd the bowl off and showed me tiny little black particles that were prevent the needle seat from sealing...
broght it back home, let it run for 3 hours....stopped it and it started right up..although it kind of kicks when I turn it over...may have a fouled plug or oil saturated air filter...
maybe I could add a little slick 50 in the oil and slick it back up?

 

[Indy4x4Fab]

i wouldnt sounds like the carb might be running a little rich or u might still have a small piece amount of leak down from the seat ether way its not a big deal. try this right before u go to shut the mower off let the engine run at idea for 15 seconds. then shut it off, u might be getting an after fire not a back fire. after fires are extra or left over fuel that has built up in the muffler, then when the engine starts back up the super heated gases ignite the fuel in the muffler and BANG, the engine starts. by ideaing the engine before shutting it down u redoose the amount of fuel that gets such threw the engine as its coming to a stop.