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Hello, I just joined this morning and this will be a long post, sorry for that. The #'s off of the engine are 126T05-3216-81-10040756. This is my daughters Lawn Boy with this briggs engine. They asked me to look at it with the problem of not staying running. I brought it home and cleaned the carb, same problem. Ordered a new carb, exact same problem. Took the flywheel of and cleaned magnets, installed a new briggs flywheel key. Same problem. Ordered a new ignition, installed it and a new plug, same problem. Installed a new head gasket, same problem. I then lapped the valves, thought one might possibly might be leaking, put it all back together. Exactly the same. It fires when you pull the rope but won't stay running. Open the choke (held open with a screwdriver) it will start but dies after several seconds and never picks up like it is going to run. I read threw 30 pages of posts but didn't see this problem. I don't know what else to try, I'm looking for advice. Thank you I went out and bought her a new mower this morning but I would like to resolve this so I can sell this mower. I drained the fuel and added new, still the same.

Well Bill I don't blame you for wanting to fix and sell... Get some of that money you threw at it back..........

Make sure the 2 bolts that hold the carb plate, not the carb itself , but the plate that the carb bolts to are tight.

Next take the air shroud off and check the intake tube bolts....... Make sure they are tight......

Did you check for valve lash/ clearance when you lapped them ??

I wish I had the mower in front of me ..........

Let us know Mon Ami ~!~!

The parts that you bought new, are they OEM Briggs or fleabay cheapies ??

If you read through the 30 pages then you should have seen the following because it gets posted 5 times a day.

Arm yourself with an in line spark tester and a can of carb cleaner.
Hook up the spark tester then remove the plug.
Spray a VERY SMALL amount of carb cleaner in the plug hole.
Pull the starter.
THe tester should flash and the engine should fire a few times.
If it does the spark timing is good.
do the same but spray the carb cleaner down the carb throat.
If it fires then the valve timing is good and the valves should be sealing.
DO the same again but this time shoot some very short shots of cleaner down the carb throat
If you can keep the engine running for 30 seconds or longer by doing this ( it will be rough ) then the problem is no fuel getting into the engine.
All the time keep your 3rd eye on the spark tester which should always flash while the engine is revolving.

That engine is going on 9 years old........ The fuel line is probably bad on the inside of it... That is common.......

Or your tank nipple is clogged up with all the old junk that E gas causes......... 3 small bolts and 1 bigger one on the side of the engine holding it on ..........

A 3 minute job to take it off to check it and give a good cleaning..............

I just had one of these auto-choke models. The problem was the thermostat/air vane system. Clean the Tstat pivot point, then spray lube. Make sure the metal Tstat arm is located between the 2 sets of marks on the black plastic air vane. Check the air vane spring, too - may be stretched out. I tested the tstat with a hairdryer to simulate muffler getting hot and watch the arm move and decrease choke.

Thank you for the replies, I will get it checked out and post back. Probably won't get to it today but I will let you know what I find.

dougand3 said:

I just had one of these auto-choke models. The problem was the thermostat/air vane system. Clean the Tstat pivot point, then spray lube. Make sure the metal Tstat arm is located between the 2 sets of marks on the black plastic air vane. Check the air vane spring, too - may be stretched out. I tested the tstat with a hairdryer to simulate muffler getting hot and watch the arm move and decrease choke.

Click to expand...

Doug,,,,, What do you mean by T Stat arm being between 2 marks ???? The L head models for the EZ start auto chokes the T Stat arm stays toward the front of the engine...... It controls the air vane arm when the engine cools down..

Let me know Mon Ami ~!~! Plus Tard ............

Boudreaux, the one I had....the air vane hook has 2 sets of marks to keep the tstat arm centered. Front to Back and Left to Right. I had to bend tstat arm a little (triangle became a little smaller) to be centered.

I checked the choke thermostat with a heat gun and it moved forward, it didn't seem to move very quickly but it did move all the way to the front. I checked the intake manifold and the bolts did tighten some. Still does the same thing however. Waiting for the spark tester to arrive to check that out. The aftermarket coil I had installed was somewhat different in shape and wouldn't let the choke vane move properly. I put the original back on, it does fire but won't keep running.

Push tstat arm forward - does spring pop it back? Is air vane spring good? Does air vane snap back when pulled forward? Is any part of tstat metal arm touching air vane hook? Is governor spring good?
Good video on auto choke... https://www.youtube.com/watch?v=YAqVcdZOZE4&t=1816s

Another test is pull air vane forward (= no choke) and tie it off with cable tie or something. Try getting it to run with starting fluid.

Bill here is a video link you might want to watch.....I have a short vid on my channel, but Non'c Bruce goes into detail on this one ........ Bruce is a very good friend of mine and a very good mechanic.....

In this video he shows the dead man cluster also..... If that's not right, off just a lil bit the mower will run run but die right away from vibration.... I have seen it happen a few times.... Skip to 6:45 and see the choke part it you want....

He explains the operation of the choke in his own words.....

Actually in my words, since I am a small engine tech,.....The air vane opens the choke when the engine is started and running....... When the engine is warmed up and running for a while then air vane spring keeps the choke open for hot starts... When the engine cools down, the T Stat closes the choke for a cold start..... Like in the video at 15:20 which is supposed to be closed since the engine is not warmed up all the way........

Like I said before the air vane arm goes to the front of the engine as shown at 3:15 in the video.......

I will post again soon as soon as you let us know something Mon Ami ~!~!

Plus Tard Mon Ami ~!~!~!

https://youtu.be/rZ90ejdim6g

Thanks for the help guys. I received the spark tester and it appears there is a spark problem. I had installed the aftermarket ignition and the symptoms stayed the same, it wasn't however able to clear the choke vane and I reinstalled the original ( with the same problems) Do you thing I need to order a new ignition from Briggs? I tested the spark tester on my log splitter and it worked fine, doesn't show spark on the 6.75 Briggs. I will wait for your reply to proceed.

Yes a Briggs coil not a flea bay coil...... You might can get a used one in your area....

Good video, thanks for sharing. This is the exact same engine as the one I am working on. Waiting on parts, I'll let you know how it goes. Thank you.

OK I installed the new coil and like always, this thing has fire some of the time. I have tried unhooking the kill wire at the coil and the same thing. There are two wires on a limit switch on the kill cable, I checked the switch with a volt meter and made a jumper to hook between the wires, still the same. Is it possible for a flywheel to go bad? It will pull a screwdriver to it on the magnets. I'm stumped again.

Not knowing what to say about coil firing sometimes ...... have you checked the muffler for carbon blockage ..??

Hmm last time I had ignition problems, it turned out that my chinese ignition coil that I purchased didn't work. I bought a proper one and that ended up being the problem.

Only thing I can suggest if it really is spark problems is what fnaguitarplayer suggests in this video - oxidation between where the coil is bolted to the housing. I've heard that's an old wive's tale, but hey may as well check just in case.

https://youtu.be/S8B7Xwpz94w?t=5m23s

Yes if you have fire some of the time then it will be 3 things.......

1 a bad ground or bad contact to the coil mounting posts..... Just put a flat bastard file across both at the same time and rub gently... Not a lot just to make shiny......

2 a kill wire with bad insulation going to ground....... UNPLUG and leave unplugged..... for the meantime...

3 Yes a flywheel magnet can go bad........ Check with a 1/2 inch combo wrench about 2 inches away to see if it draws it in ETC ETC.........

I will try these suggestions today, thank you.

Boudreaux In Eunice La. said:

Yes if you have fire some of the time then it will be 3 things.......

1 a bad ground or bad contact to the coil mounting posts..... Just put a flat bastard file across both at the same time and rub gently... Not a lot just to make shiny......

2 a kill wire with bad insulation going to ground....... UNPLUG and leave unplugged..... for the meantime...

3 Yes a flywheel magnet can go bad........ Check with a 1/2 inch combo wrench about 2 inches away to see if it draws it in ETC ETC.........

Click to expand...

And don't forget an internal short in the coil, or a dry joint in the coil or a faulty trigger module.
Have seen all 3 on cheap ebay coils customers had fitted to their mowers before they gave up & brought them to me.

I have put 3 different coils on this thing and all 3 do the exact same thing. I cleaned up the coil mounting posts and still the same. I've come up with several new names for this mower but don't think I can post them on a public forum. I have left the kill wire unplugged so that isn't the problem. I could have bought a new engine and installed it for what I have invested in this one. Now I am determined to figure this out (I'm in no rush at this point) it can take all winter. The flywheel will pull a 1/2 wrench to it from 2" away but this is about the only part I haven't tried at this point. This is an electric start engine but the electric start hasn't been used since new. The battery would need replaced to used it but it will spin the engine, I charged it enough to make sure it will work. Are these flywheels different? I have an old flywheel from an older briggs without electric start. Please let me know if you can think of anything.

some of the larger models have a small on off valve under the tank. Be sure it is in the on position. First device I bought used had one and took me awhile to figure it was there because it was hidden up under the tank. Also the fuel pumps on many engines just go bad. They use a small flap as the valve and when the gasket ages and warps the fuel pump no longer pumps. Although really good with larger engines, I am just a layman with these small engines but I have seen things like this. A dirty or wet air cleaner can cause all sorts of problems too.