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

[BGood]

I adjusted the governor linkage according to the procedure previously posted from the Tecumseh service manual (thanks Rivets), and tried mowing first with the repaired original carb, then with the replacement eBay carb.

The mower still has a tendancy to stall in high grass and is difficult to restart when warm. When starting to stall, engine RPMs drop, I back the mower off from the high grass using the r/c electric motors, and about half of the time the gas engine RPM continues to drop and eventually stalls, and about half of the time the engine RPMs slowly increase and eventually recovers. When there is a stall and I look under the mower expecting to find grass wrapped around the blade, I am surprised to see it is relatively clear.

I wonder if I adjusted the governor linkage correctly. I untightened the torx screw, moved the arm rearward until I felt resistance, then retightened the torx screw. I'm not sure if I should try moving the governor linkage arm more forward or backward. Should I also adjust the idle set screw? On the old carb it is in about 2 threads and on the replacement carb it is in a little more, about 3-1/2 threads.

Not sure what to do. I can't swap out the 6.75 hp Tecumseh engine for the 12 hp riding mower engine because the robot chassis is built around the Craftsman mulching mower. Another factor may be that the mower blade that came with the used Craftsman mower does not appear to be a mulching blade. Would swithching the blade out make a big difference?

Thanks for any ideas

 

[Rivets]

What have you set your top end governed speed at. Should be between 3200-3300 RPMs. If it is too low your engine will not keep up when it encounters a load. I’m assuming you opened the idle jet as I suggested earlier. This needs to be open as it supplies extra fuel to engine when you enter that long grass and the governor kicks in.

 

[sgkent]

have you tested compression on this mower? I have seen engines that have low compression refuse to recover once they start to stall. Meaning, the tall grass starts the stall, but when you back out the engine should recover quickly. The other cause can the mixture. As an engine loads down, the intake air flow slows and that affects mixture. Try a little richer, if that makes it worse, go a little leaner.

 

[fredeharle48]

I’m planning a project to build a remote controller lawn mower, relatively small scale PoC first to test Small scale will be a basic chassis setup in a skid-steer configuration with 2 drive wheels at the back and 2 idle wheels at the front (with future goals of changing to tracks); current wheels I’ve found are 120mm dia and total mass estimate will be around 15kg. It will be controlled by an r/c tx/rx feeding PMM into a microcontroller (Either Arduino or ESP8266… haven’t decided yet) which in turn signals a motor controller to feed power to either drive wheel. It needs to be capable of variable speed and run in forward & reverse. Based on reading other people’s similar projects here I think the overall concept will work but they often used 2nd hand wheelchair motors which I’ve not been able to source yet in Australia so looking for something more off the shelf. I’m good with microcontrollers & programming but new to motors & robotics in general.