Engine runs rough and backfires under throttle

Visuals are difficult according to an electrical guru on line because the hottest sparks are almost invisible. Try holding a piece of paper back of the removed plug for highlights. Don't know if 10 minutes gets you to operating temp . Unfortunately transistorized spark modules cannot stand over about 250F. Then the little guys fail although they may work at cold for a while. Sometimes you can actually cool them after they stop and they will again work for a while. Manufacturers know this and heat sink the modules by location. But IMO severe heat as in low/no oil, fan clogged will fry 'em.
 
I use a colour tune in these circumstances, excellent piece of kit and at $ 30 cheap as chips. allows you to look into the cylinder and check for lack of spark or lean burn conditions.'Failing that an inline tester works well if the engine will actually slputter to a stop.
If you see flashes and get not bangs to go with them it is a fuel problem ( valves, timing etc )
If you see no flashes as the motors winds down then the ignition is the problem.
Considering the price of the ignition modules, cheap as chips.
 
I have the same problem- Kohler SV715 courage 22 hp that I've had for 5 years. First issue ever. Runs great and then after about 10-15 minutes starts running rough with occasional backfire especially under heavy load. Mice had chewed wiring to cylinder #2 spark plug/ignition module. Replaced wiring harness and ignition modules on both cylinders. Also replaced fuel filter and pump. Engine really came to life and could mow for a while, but now back to original problem. Discovered sloinoid was not clicking when turning key to first position. Rebuilt carburetor and solinoid works. However, problem remains. I can get it to run, albeit erratic, by playing with the throttle- moving it into choke mode for a brief time and then back to running mode. One thing to note, I did not realize that cylinder 2 was messed up because of mouse issue- so basically cylinder #1 was carrying the load.

Any feedback is greatly appreciated. Thanks...
 
jspringky said:
I have the same problem- Kohler SV715 courage 22 hp that I've had for 5 years. First issue ever. Runs great and then after about 10-15 minutes starts running rough with occasional backfire especially under heavy load. Mice had chewed wiring to cylinder #2 spark plug/ignition module. Replaced wiring harness and ignition modules on both cylinders. Also replaced fuel filter and pump. Engine really came to life and could mow for a while, but now back to original problem. Discovered sloinoid was not clicking when turning key to first position. Rebuilt carburetor and solinoid works. However, problem remains. I can get it to run, albeit erratic, by playing with the throttle- moving it into choke mode for a brief time and then back to running mode. One thing to note, I did not realize that cylinder 2 was messed up because of mouse issue- so basically cylinder #1 was carrying the load.

Any feedback is greatly appreciated. Thanks...
Click to expand...

Other thing to check is that fuel tank vent hole (tiny hole on cap) is working. It sounds like as the mower runs and gas leaves the tank, air is not replacing the volume and creating a vacuum which then limits the flow of fuel after that. Once the issue starts, try loosening the fuel cap a bit and see if it stops...hope this helps someone!
 
Unplug one of the plug wires and try to start, then try it the other way.
Tell us what you find.
 
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