Mtd yard machine will shut off when you change speed control to faster

SOURCE: 6 yr old mower starts, won't run

sounds like a plugged high speed jet in carb - you can attempt to prime again , push at least 7-8 times - once it fires continue to push primer to keep running - it may clear out the carb if this doesnt work the carb will need to be removed and cleaned

SOURCE: oil change

if this model has a fill tube on it- turn the unit on its side to drain.

SOURCE: I HAVE A MTD YARD MACHINE 12A446B729. RUNS FIVE

was having the exact same problem with my 6.5 hp Toro lawnmower with a Tecumseh engine. The engine would start up okay but after a few minutes of mowing, the mower would start missing and eventually shut down. I would pull and pull and pull on the starter rope, getting angry and frustrated and eventually going back in the house to let it cool down.

I looked up all kinds of information and I finally decided it was a bad coil (something about the resistance being low when the mower wasn't hot and then when it heated up the coil would conduct enough electricity to somehow make the engine shut down.)

I called a local shop and wanted to get an estimate on replacing the coil. I have no clue about engines so I dared not get into the guts of the mower myself. He told me to check the gas cap. HUH??????

He told me to make sure there wasn't a part missing out of it. I thought, what the heck would a gas cap have to do with the engine shutting down. Well, apparently there is a mechanism on these caps that prevents a vacuum from pulling on the fuel system and my gas cap indeed had a part missing. To verify this, I cut the grass for about 5 minutes. When it started to run rough, I took the gas cap off to allow pressure to escape from the gas tank and voila! it started to purr like a kitten.

So, I'm only out $4 for a new gas cap and I'm as good as new. Man I wish I was more mechanically inclined so I hope your problem is as easy to solve as this one.

Hope this helps!

SOURCE: lawnmower wont start

Possible Causes Corrective actions
Unit will not start Control handle is not engaged Engage control handle
Spark plug wire is disconnected Connect spark plug wire
Fuel tank empty or stale fuel Replace with clean, fresh gas
Blocked fuel line Clean fuel line
Faulty spark plug Replace, clean, or adjust gap
Engine flooded Wait to restart, do not prime
Air filter filled with dirt or debris Replace or clean air filter

SOURCE: Yard Machines - Won't shift into gear

The problem most likely is the shaft on which the interlock slides back and forth on inside the transmission. The yardmachines have a continous spinning shaft which ends in a bevel gear. The is an interlock plate which is connected to the Forward Reverse shift lever, this plate slides back and forth and either engages the forward gear or the backward gear. This shaft is most likely galled up, preventing everything from sliding the way it needs to. This is not a difficult thing to fix if you are somewhat mechanical. Disassemble the transmission and check if everything slides