GT18 carb problems

First off get rid of the e3 spark plugs they are half of your problem install some NGK or Champion plugs. It sounds like the float is set wrong is it leaking gas static or when running does the engine start right up or does it require lots of cranking?
Believe me I know about those E3 plugs had a 11 hp Briggs that would not start for crap run terrible I did a carb kit adjust on the carb until I thought the cows would be coming finally check the spark plug it was an E3 plug it looked good but I installed a new NGK and the engine started right up and runs perfect now I also have what looked like flood ing but it was from choking trying to get it started.
Took the E3 to my spark plug cleaner tester and after cleaning and gaping it tested it it would fire fine at 60 PSI but at 80 psi was intermittent and at 100 psi did not fire at all but the spark was jumping out side the plug reduced the gap to a tight 0.25" before it would fire at 100 psi. Others have had the same problem with these plugs.
GB in MN

Wow, I didn't know e3s had those kind of problems. :thanku: Maybe the magnetron ignition can't provide enough juice compared to a reg. ignition coil.

I'll try switching plugs tommorow, and also try to make a video of my problem. I'd like to show how a LOT of gas is coming out of the tube near the choke, seems like it would run rich.

Maybe I didn't mention this before, but the motor will only run on one choke position, and it's not full, but pretty close to it. Full choke is too rich and the motor starts smoking like crazy and sputtering.

Hi sound just like my Briggs, was driving me crazy because I knew the needle seat was not leaking but it would not start without choking it and then there would be gas leaking and yes it would not run with out choke till it was warmed up, I adjust the jets and it seemed to run good shut it off and 5 min later it would not start had to go thur the same thing finally I changed the plug and it run like a dream, the Magnetron provides good spark. My test has very strong spark and the E3 plug just did not fire at 100 psi the spark would jump from the electrode along the insulator to the base of the plug about a 1" gap but nothing at the electrodes of the plug.
GB in MN

Update:
I adjusted the idle today and got it to run without choke. With choke off, it still surges (at any RPM above idle), but with 1/2 choke it smoothes out. I try to show this in my video.
If only it had an adjustable main jet! Can an adjustable one be fitted to these emission carbs with only an idle adjustment?


Video of my problem:
http://s306.photobucket.com/albums/nn241/foodman500/?action=view&current=briggspos.mp4

Interesting. The fact that it smooths out with the choke at 1/2, tells me that it is running lean. But it does not have an adjustment?

Has the air filter been changed to a different type? From foam to paper for instance? I'm wondering if the air filter is not as restrictive as originally designed.

Does it change under load?

There is no way to adjust the main jet, so they say in the manual. It's an allen screw that goes all the way in, no spring on it.


The air filter is the same as the old one I just added the foam pre-cleaner.

Under load it still does the same thing.

I'm still stuck.
:dunno:

I have not had this problem.... but just thinking.
1. Air leak - Carb to manifold - Manifold to engine.
2. Fuel pump (intergical to carb)
3. Govener linkage.

I'll be watching as I have the same engine.

http://www.youtube.com/watch?v=otUtHEiFkCk

larrybl said:

you are running way too lean then.

Click to expand...

Not so, Larry. I'm not saying it would ignite, I'm only saying it is way too hot for me to even think about trying to spray the area with starter fluid. That's why I suggested oil. Oil will seal the leak (if it's a gasket) for a short time with far less likelyhood of a fire. Messy though. My engine is a one lunger and the carb is only 2"-3" from that hot exhaust pipe and muffler. I painted the muffler with black 1200 deg. high heat paint and it quickly burned it to a white powder. I don't know the exhaust proximity to the intake on the engine in question.

I am using JB Weld on my muffler till I can afford a new one. This is a "single lung" Kohler 321. I would have a lot of problems if this ran red.

larrybl said:

I am using JB Weld on my muffler till I can afford a new one. This is a "single lung" Kohler 321. I would have a lot of problems if this ran red.

Click to expand...

Pretty engine.

The operative word here is "almost"....and it's not the engine, but the elbow in the exhaust system and bottom of the muffler.

When I said my engine would likely be a ball of flame if I sprayed starting fluid on the intake manifold, while running, to look for air leaks, it is because starting fluid is much more volatile than gasoline and my intake manifold is right alongside the exhaust manifold. You can see the high temp paint (1200 deg. spike and 600 deg sustained) is thoroughly burned off of the elbow and bottom of the muffler. It must get over 600 deg. to do that. And (as can be seen in the picture) the spark plug wire runs right alongside the intake manifold. A 40+ year old spark plug wire can leak current to ground (spark) along its length.

I wouldn't spray gasoline on a hot, running, engine, especially in the area of the intake manifold of this engine. Gasoline has an autoignition temperature of 475 deg F. meaning it will auto ignite at 475 deg. F without and external ignition source. Starting fluid has an even lower autoignition temperature of around 325 deg. F. (depending on content).

In my view, the result of spraying either (gasoline or starting fluid) on my running engine, is not a pretty one. :Stop:

Good news: the problem turned out to be the idle mixture screw, I just made it richer and the surging went away. The idle circuit must be connected to the non adjustable high speed circuit. I also found some crud in my gas tank after draining all the gas out. Now she runs great.
:thanku: for all the tips guys, now I feel a lot better about this carburetor.

One thing I'm still a little confused about: as someone said before, how does the governor linkage affect the mixture?