You are here:

Small Engines (Lawn Mowers, etc.)/simplicty sunstar 18hp kohler


QUESTION: I have simplicity sunstar 18 hp tractor .the motor runs fine until after about 20 minutes under load the engine will shut off. I can wait till it cools off about an hour or more and it will refire and run fine for another 20 minutes and shut down can leave mower with pto on and it will not shut down it will only shut down when mowing. I have replaced seal in motor 'changed oil sending unit,,bypassed circit breaker, when mower shuta down there is no fire on plugs. motor will turn over but will not start.thank you randy duckworth in carolina

ANSWER: What is the model number of your Kohler engine?  You can download the service manual from Kohler...for free!

In cases like yours the first thing I would do is isolate the engine igntion system from the mower wire harness.  This usually just involves dis-connecting one wire...just need the engine model number to help you find the one wire.


---------- FOLLOW-UP ----------

QUESTION: Kohler Magnum 20, Model Number M20S
Serial Number is 2129008036
Spec number 49544

Service manual can be found at the address below:

Page 8.3 describes how to check the ignition module but you have to remove the engine sheet metal to access the module.

An easier way to isolate the ignition module from the mower chasis is locate the kill lead wire connected to the engine.  There will be a wire from the ignition module to a terminal on the engine.  The terminal allows the mower manufacturer a place to connect the shut-off wire.  It is usually only ONE wire and either a spade or screw terminal.

I would dis-connect this wire and use the mower.  NOTE you will NOT be able to shut-off the mower with the kill-lead dis-connected.  You can just close the choke and flood the engine to turn it off or you could pull each spark plug wire to stop the engine...I'd use the choke.

Let me know if the mower will run more than 20 minutes with the kill-lead dis-connected.

Small Engines (Lawn Mowers, etc.)

All Answers

Answers by Expert:

Ask Experts


Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

©2017 All rights reserved.