Craftsman mower robot - Governor/choke issue - Stalls under load and won't restart when hot

[Rivets]

I’ve worked on these carbs a couple of times in the past and know what I’m talking about. These other guys need to read the manual. Sgkent, you are totally wrong. The OP has a Series 11 carb. That is the idle jet which has one hole vertically and one hole horizontally. They both need to be open. BGood, I recommend that you open the bottom oriface and your problem will be solved.

 

[sgkent]

I’ve worked on these carbs a couple of times in the past and know what I’m talking about. These other guys need to read the manual. Sgkent, you are totally wrong. The OP has a Series 11 carb. That is the idle jet which has one hole vertically and one hole horizontally. They both need to be open. BGood, I recommend that you open the bottom oriface and your problem will be solved.

think about what you just said. He is saying that a copper wire will not go all the way thru the jet from the hole on the bottom to the left hand side of the jet in the photo. He should not try to open the jet all the way thru to the left hand side. It only needs to be open on the three holes so go flame someone else.

 

[Rivets]

You better stop working on any Tecumseh engines if you believe what you just posted. If you can read and understand pictures, take a look at the service manual I posted on how these carbs work. This jet has two operations, large horizontal holes will feel fuel straight through to the high speed circuit. The small vert hole, which in this case is plugged, feeds the idle circuit. That’s why it is called the idle jet. It’s size is .017” and needs to be kept Ed clean for both the starting and idle circuits. If you don’t understand what the manual says, maybe this one has more pictures to help you. http://www.tecumsehcarburetorguide.com/how-to-guide/

 

[BGood]

well for one, you dont have any kind of choke setup...you have a primer bulb setup designed to place gas into the carb intake tube to allow the engine to start from the extra gas in the tube...you dont have autochoke or a choke flap at all...second...when does it stall out and how steep is your hill...are you going up the hill and this happens or down...if down hill...depending on the slope of the hill...youll experience fuel starvation because the gravity feed fuel from the tank is lower than the carb...you might want to consider remotely mounting the tank higher than the engine to insure the fuel always flows to the carb going up or down a hill...also check the fuel cap vent hole to make sure its got good air venting to take up for fuel loss when running...i suspect your biggest problem is the slope youre trying to cut...

Thanks for your comments, skiman. All of the stalls have been in thick grass on relatively flat terrain when the mower has bitten off more than it can chew. So I don't think that slope or up/down attitude is the issue. Also, I've found that the mower's light weight (135#), wimpy wheelchair motors, and poor wheel-ground traction preclude mowing uphill. Downhill is much easier. Not sure how to test the fuel cap vent hole.

 

[BGood]

I read through the Tecumseh references from Rivets and while much of the material is beyond my mechanical experience, I suspect that the interior cavity of the idle screw I removed may be more involved that I first thought. While the thin copper wire I could not push through the end orifice to the lateral holes was maybe 24-26 gauge, when I used a thinner tapered needle I could see the tip of the needle through the lateral holes but could not push it in any further. This suggests to me that the cavity is tapered and too small for the solid copper wire to pass through. Also, the lateral holes are different sizes. What this all means I'm not sure, but the repair manual does provide an adjustment procedure for the governor arm which I'm going to follow when I put everything back together. Hopefully with no parts left over. Thanks for the help!

 

[Rivets]

As I posted the bottom idle jet hole is .017”. Because I have them I use a micro drill to clean this jet when it becomes clogged. I start with #80 and proceed up to #78. Sometimes I need to go to a #77, which is .018”. You must be extremely careful that you don’t break the drill off in the jet, yes I’ve done this more than once.

 

[BGood]

Following up on my tune-up progress with the stalling and hot restart problems with my robo mower gas engine, I've been addressing a variety of deferred maintenance issues that came along with purchase of the old mower used a a basis for the robot. Besides the carb diagnosis, idle jet cleaning, and governor adjustment already discussed, other issues include blade sharpening, oil change, spark plug, and ordering a cheap replacement carb if my DIY repairs failed. At this point the replacement carb has arrived and I discovered that the recommended spark plug gap is actually .030" rather than the larger .045" I re-gapped to. This makes me wonder if the oversize spark gap might have contributed to my warm restart problem?

But now that I have a new replacement carb in hand, have regapped the spark plug to the .030" spec, and concerns about the knowledge and specialized tools I don't have for a complete carb rebuild, my inclination is to install the replacement carb and make the governor adjustment described below from the repair manual Rivets provided.



Does this make sense to you more experienced gas engine guys? Assuming it does, is there any additional guidance you can suggest for the governor linkage adjustment?

Thanks.

 

[Rivets]

Before installing the new carb, I would install the properly gapped plug and adjust the governor. If that doesn’t solve the problem then I would install the carb.

 

[sgkent]

really. I never knew a small mower that would not stall on tall grass. Around here every spring I have a few neighbors who let the grass grow too tall. You can hear them on Saturdays in late spring, rrrrrrrrrrr thump. whiiiish, whiiiiish, whiiish, damn mower, rrrrrrrrrrrr, thump. Son of a bitch mower. whiiiish whiiish whisssh, rrrrrrrr thump. It is like a chorus of cicadas from all the yards that let it get too tall.

 

[bertsmobile1]

Larger gaps = higher resistance
Higher resistance tends to force the spark to run down the side of the electrode at lower speeds
Usually it makes the engine harder to start cold .