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Hello, I have a problem with a Toro Timemaster Model #: 20199 with a briggs 190cc #121S020130F1 engine.

The mower when it is cold runs horrible. I noticed that the auto choke linkage and arm on the carb flaps and flutters back and forth very fast and violently. This linkage goes to a thermostat on that muffler to the carb. If I hold the linkage in the choke OFF position the mower runs great and has good power but when i dont hold it the choke flap opens and closed at a very fast rate like its flapping in the wind.

Could this be a faulty thermostat, linkage, carb?

IT does sounds like a faulty thermostat. The replacement PN is 798938 . or the carburetor could be missing the choke spring. Here is image of the carburetor showing the spring. The problem is that Briggs don't sell the choke seperately from the carburetor.

The choke return spring is part number 798900.

Ahhh after downloading the IPL from Briggs I found the choke listed but it is list as 799179 and not as Rivets listed as 798900. My fault for trusting outside vendors instead just downloading the IPL from Briggs in the first place.

They do appear to be two different springs.

It looks like all springs and linkage are there. Here is a video of the choke lever going crazy I have to hold it with my fingers to keep it from moving but as soon as let go it goes crazy again.

could the linkage be causing this issue? The governor spring post was bent inwards pretty bad and was down on RPM. Looks like someone hit a low branch with it. The linkage is right next to the governor spring. Makes me think.

Star is correct, I used the wrong engine type number.

I never seen an engine doing that to the choke. It as something bouncing the throttle linkage but it is not moving that I can see. Now I am curious as to the cause too. Hope you find the cause and let us know what it is.

I had that problem a few weeks back.
I ended up buying a new carb but for curosity I swapped the spring from the new to the old and that stopped the choke flapping .
The linkage from the auto choke had also been bent a bit from running into things so I bent it back to tighten the Off position and that cut down the amount of flapping a lot but it did not stop till the springs were swapped.
This is the one that was running rich

If the choke is bouncing while the engine is running, you need to tighten the spring tension by moving the tab the spring is hooked to, in toward the engine. This spring is designed to close the choke when the end is closed.

I don’t seen any adjustments I can make to the choke spring. it is attached to all plastic.
Here are some pics.

Sorry here they are.

Here is a better video of the problem, it only happens when the mower is cold or sits for around 20-30 min. It happens as soon as the blades engage the choke goes crazy

The choke goes gar gars because when the blades are engaged the throttle opens up and more air is sucked past the butterfly which tends to close the choke , which stretches the spring which then pulls the choke back and the air pushes it closed , the spring stretches and thus they cycle continues.
Cut 2 turns off th short ens of the spring then bend the next one out 90 deg to fit over the pin

bertsmobile1 said:

The choke goes gar gars because when the blades are engaged the throttle opens up and more air is sucked past the butterfly which tends to close the choke , which stretches the spring which then pulls the choke back and the air pushes it closed , the spring stretches and thus they cycle continues.
Cut 2 turns off th short ens of the spring then bend the next one out 90 deg to fit over the pin

Click to expand...

Just cut the spring to shorten it but still no change. I cut another 2 off and still no change unfortunately.

Any other ideas before I fire the parts cannon at this?

Does anyone think this is a governor issue? I just came across this video and it looks like the same thing is happening.... Fast forward to 6:05.

My neighbor gave me his non-starting TB PW 020381 with Briggs 12S912, same as above video. I found exactly the same thing as above. I needed camshaft, gov/oil slinger, timing gear, gaskets - it was over $100 in parts. I said screw it, parted engine out and found another for good pump PW. But if all you need is gov/oil slinger and gasket - would be worth it.

Update, new choke spring cam today and still same issue.

After that I took the engine off and took off the crankcase cover to inspect the govenor. Everything looks fine inside. Gonna order a new gasket and put the engine back in i guess...

This is turning into a huge mystery and getting frustrating.. Any other ideas?

I’ve worked on dozens of these units and don’t understand what is going on. I’m going to have to get to the shop to see what a new unit looks like. Something tells me you don’t have something hooked up correctly. Will get back to you as soon as possible.

Rivets said:

I’ve worked on dozens of these units and don’t understand what is going on. I’m going to have to get to the shop to see what a new unit looks like. Something tells me you don’t have something hooked up correctly. Will get back to you as soon as possible.

Click to expand...

I really appreciate that. I did buy this mower used a few weeks back so anything is possible at this point.
If you need me to take more pics of something specific let me know and I wil upload then ASAP.

Got everything put back together fully with a new crankcase cover gasket and went out to test it again to see if messing with the govenor did anything. Still does it (choke flapping) but once it warms up enough it to the point where the thermostat on the exhast fully opens and pushes the arm/linkage it runs beautifully..

You might need to bend the connecting wire from the auto choke to the choke in order to put more pressure on the choke to open & not flap.

Wondering how this turned out as I'm having the identical problem and I have a hypothesis if you'll indulge me.

I'm having this same issue with a Briggs power washer. I'm starting to think it's a faulty auto choke. I'm trying to find out how long it should take for the auto choke thermostat to fully actuate but can't seem to find the information. I've timed the one I have and it's anywhere from 3 to 4 minutes, which seems excessive.

It appears as if the choke spring holds the choke closed, not open. So a tighter spring may not solve the problem. The O.P. said that this happens when the blade is engaged. I have the same symptoms when I engage the water pump.

There's no throttle on this so it runs full. When not under load, the governor is putting closing pressure on the throttle, which in turn, puts pressure to open the choke (the way it's designed with the oblong interference linkage). When it comes under load, the governor releases the pressure and the governor spring opens the throttle, which takes the pressure off the choke lever allowing the choke spring to close the choke unless the thermostat is putting pressure back on the choke arm.

This appears to start the oscillation as the airflow is interrupted and the governor tries to stabilize things. Because of the way it's designed, this starts a sort of oscillation causing the choke to flap, until the mechanism of the thermostat kicks in and puts permanent pressure, holding the choke open. If I take a screwdriver, hold the choke open, and then engage the water pump, everything runs perfectly. This appears to be why after it warms up (almost 5 minutes), everything is fine. But I think the problem is that the thermostat choke is faulty in some way and taking too long to fully heat up and engage. Does this make sense?

Can you take a couple of pictures of the linkage. Some thing doesn’t sound right, but I’m not standing there to see how it’s working.

Certainly. Top down, front and then the front with the throttle held closed (Order of photos).
The default position when off is throttle wide open, choke closed. All handled by the springs you see. Once the engine starts and goes up to RPM, the governor closes the throttle a bit because there's no load. The closing of the throttle pushes the choke open quite a bit. So it runs fine at full throttle during this time. Once under load, the governor pushes the throttle open which appears to allow the choke to close. I apologize for being redundant. It's just so confusing to me so I keep saying it over and over again to make sure I'm saying what I'm thinking. Once up to temp, the thermostat pushes against the choke's spring tension and holds it open. But that takes a substantial amount of time, several minutes.

By they way....
Briggs: 020515
Serial 1020259701
Engine: 111P02-0114-F2
Code: 12090762
Just in case it's helpful.

Stihleer said:

Got everything put back together fully with a new crankcase cover gasket and went out to test it again to see if messing with the govenor did anything. Still does it (choke flapping) but once it warms up enough it to the point where the thermostat on the exhast fully opens and pushes the arm/linkage it runs beautifully..

Click to expand...

You just answered your question. It needs a new thermostat. You said once it warms up it runs perfect. Something in that thermostat is not working properly. Stop messing with springs and governors.

slomo

Any way to rig up an old school choke cable?

slomo

If the governor is not adjusted properly, it is going to bounce. Have you checked the governor top speed, if the governor is not adjusted to the recommended top speed (spring controls this) the governor will pushed the throttle open. More than once I’ve seen where customers have played with the governor to get more speed, screwing up the carb.

Once it warms up fully, it runs fine.

slomo

Which could mean that the linkage may have been bent closed, not allowing the thermostat to push it open, or hold it tight again spring tension at startup. I will agree that the thermostat could be bad, but we are being given the tail end of the problem. Has this happened over time or all of a sudden. Remember we cannot see what is happening, which to me means checking everything before throwing parts at it. He can do what he wants, just want to let him know he has options. Governors do go out of adjustment and linkage do get bent by accident, on purpose and by gremlins.

The one I'm working on is dialed in per my Tach. My apologies if this got confusing. I piggybacked on this post because it had kind of fell off and I had an identical problem. I thought I may be able to help as well as solve a similar problem I'm having. Based on the design of both machines and the symptoms, I would agree that the choke thermostat is the culprit. I was just looking for some confirmation.

Does anyone have an opinion on how long it should take these thermostat type chokes to fully actuate? The machine runs at full RPM once started. I don't have a lot of experience regarding the elapsed time for these to fully engage. I was hoping to find something in the manual like...." let it warm up for x or y minutes..." but there's nothing. Most of the auto-chokes I've worked on have been the air vane type.

Wasn't the choke. Was able to get a new one and still have the same "problem". Maybe it's not a problem. I think it's just this thing needs time to warm up.

Rivets said:

Which could mean that the linkage may have been bent closed, not allowing the thermostat to push it open, or hold it tight again spring tension at startup. I will agree that the thermostat could be bad, but we are being given the tail end of the problem. Has this happened over time or all of a sudden. Remember we cannot see what is happening, which to me means checking everything before throwing parts at it. He can do what he wants, just want to let him know he has options. Governors do go out of adjustment and linkage do get bent by accident, on purpose and by gremlins.

Click to expand...

True that. Hard to see from a video of the entire ball game.

slomo

I can't speak for the O.P., who posted the video, but the machine I'm working on has an intact linkage and properly set governor. It came to me after a leaky carb upon the first gas of the season so I never saw it run before personally before that. But I'm told it was running fine. About a year old with only a couple hours on it.