[Ruritanman]

Hello, OurRuritan club has a Gravely Promaster 300 with a Kohler Magnum 20 engine, bought used 3 years ago, date of manufacture unknown, 680 hours on the meter.
Works great, except that when it's first started, the engine will cut off when the brake lever is released, and then reignite if the brake is immediately reapplied, causing the engine to backfire thru the muffler. As the engine warms up, this problem goes away, but then when I hit the go forward pedal, the engine will cut off til the pedal is released. As the mower warms up more, feathering the forward pedal will get it going til the problem disappears for that time of operation.
Lately, the engine has been momentarily cutting off during normal operation.
Any suggestions are greatly appreciated.

 

[Mark / Ohio]

Sounds like maybe ignition problem with weak spark or an intermittent electrical issue loading down the kill wire to the ignition.

You can find an online engine service manual for it here:

Kohler Engines: Magnum: Series Landing: Engines

You might find a Gravely online or paper manual for it here:

manuals

Ariens Order Owners Manuals

Looking in the engine manual there is a single coil that feeds both plugs. So if nothing seems to be shorting out the kill line into the coil (wire shorting against the frame, bad relay, bad safety switch, etc), the coil would be my guess as the culprit.

 

[Ruritanman]

Thanks Mark, will check out the wires for shorts and, most likely, the coil, as the ignition cutting off goes away as the engine warms up.
Ruritanman