Briggs Powered Toro Lawnmower

[Dale_W]

It's the 6.75 gross torque self propelled lawn mower.
Engine is 126T02-0220-B1 with the automatic choke

Engine starts on first pull, but the Spring-air vane part #790849 wont hold the choke closed.
Wind off the flywheel pushes the air vane and opens the choke too soon.
Engine dies.

I put in a new spring. same problem. Put both springs on - same problem.

What am I missing here?

Thanks
Dale

[bgsengine]

It's the 6.75 gross torque self propelled lawn mower.
Engine is 126T02-0220-B1 with the automatic choke

Engine starts on first pull, but the Spring-air vane part #790849 wont hold the choke closed.
Wind off the flywheel pushes the air vane and opens the choke too soon.
Engine dies.

I put in a new spring. same problem. Put both springs on - same problem.

What am I missing here?

Thanks
Dale

viewtopic.php?f=3&t=3134#p22278
(rather than repeat myself)

[KE4AVB]

Thermostat not holding choke partially closed.

Spring only meant to hold choke close at start-up then air vane pushes against thermostat arm; otherwords, the spring is not meant to keep the choke close while running, it is the thermostat job until the engine warms up. This allows the choke to partially open so the engine doesn't flood out. Either the thermostat has failed [or missing mounting screws or completely AWOL] or choke air vane is broken at the thermostat arm capture area.

Also need to verify that you don't simply have a carburetor problem.

[Dale_W]

Thank you both. I need to learn how to post photos here.
KE4AVB, you hit it right on the head. The vane immediately fly's forward, opening the choke on the cold engine.

If the vane was somehow captured by the choke, the vane could then only move forward as the choke coil warms up, instead of
flying forward as the choke remains. If the choke could hold the vane back until it warmed up and moved forward, it would work fine.

I need to hit the diagrams and see if the vane should attach to the choke. Maybe there is a part missing. I see the index marks on the plastic vane.
So on a cold engine it seems adjusted.

I'll keep you posted.

[bgsengine]

Thank you both. I need to learn how to post photos here.
KE4AVB, you hit it right on the head. The vane immediately fly's forward, opening the choke on the cold engine.

It's supposed to. Choke should only be for starting engine.

If the vane was somehow captured by the choke, the vane could then only move forward as the choke coil warms up, instead of
flying forward as the choke remains. If the choke could hold the vane back until it warmed up and moved forward, it would work fine.

I need to hit the diagrams and see if the vane should attach to the choke. Maybe there is a part missing. I see the index marks on the plastic vane.
So on a cold engine it seems adjusted.

I'll keep you posted.

Need to service carburetor or find air leak,if it won't stay running after start-up. Choke adjustment is there to prevent over-fueling on hot restarts. (holds choke slightly open to full open depending on temperature)

[KE4AVB]

I admit I have only seen a couple of this version and more the wire linked version. But I here I have rarely see push mowers anymore. Only one showed up last year.

Oh I wish I had save the info I seen on this choke system back in 2015.

[Dale_W]

Need to service carburetor or find air leak, if it won't stay running after start-up.

That makes good sense. That will come next. I'll keep you posted. Thanks again.

[Dale_W]

Follow up. The mower starts/runs just fine now.

I had previously sent this carb thru several ultrasonic cleanings.

Last night I took the carb off again, ran torch tip cleaners thru all the passages. Then followed up with carb spray.
That must have cleaned it up enough to work properly.

At cold stop, the air vane spring holds the air vane and keeps the choke closed. The second the engine starts, the wind off the flywheel pushes
the air vane away from the Thermostat arm, and opens the choke.
Now that carb is clean, enough gasoline gets thru, and there is no hunting/surging.
As the engine warms, the thermostat arm moves forward and keeps the air vane / choke in the open position. No choking on hot start.

You guys were right. Carburetor was not clean enough to let a cold engine run properly.

Thank you for your help. (again)

Dale

[creia]

Thanks for the follow-up Dale. That is how we can ALL learn from others experiences. As good as ultrasonic cleaners are (we have been using them for over 10 years now), you still need to probe all passageways and orifices. Like you, we also use carb cleaner after the ultrasonic to further purge any loosened debris, which also serves to remove any water remaining from whatever cleaning solution you are using. I know some use compressed air for this, but I believe carb cleaner does a better job.
Michael

[wristpin]

Thanks for the follow-up Dale. That is how we can ALL learn from others experiences. As good as ultrasonic cleaners are (we have been using them for over 10 years now), you still need to probe all passageways and orifices. Like you, we also use carb cleaner after the ultrasonic to further purge any loosened debris, which also serves to remove any water remaining from whatever cleaning solution you are using. I know some use compressed air for this, but I believe carb cleaner does a better job.
Michael

Not only does carb cleaner do a better job but it doesn’t risk blowing the needle seat across the shop!!
It’s interesting that when I was learning the job xxxx years ago, shop manuals carried warnings not to poke wire etc through jets and fuel passages - now Honda and others sell a nice set of assorted jet cleaners purpose made for the job.