Have a GX690 that runs rough after running with a load for aprox 10-20 mins. Pops and pops and sometimes it almost dies.
Things I’ve done so far:
-tested ignition coils, readings were a bit high but still the same. .08 ohms primary side, 12.3ish ohms secondary side
-replaced spark plugs
-disassembled carb and cleaned jets
-cracked fuel tank lid to vent it more
-re gapped ignition coils per Honda spec to fly wheel.
-adjusted valve lash per Honda spec
Things I’m considering:
Replacing the ignition coils
I just had a similar problem with my 690. Running rough and bogging down under a load. One of the coils was bad. I know you said you check their resistance but if you have one of those inline spark plug testers, the kind with a little light bulb in it, plug that in and see if you’re getting spark on each cylinder. I ended up having to replace a coil.
A coil is likely going out. They’ll probably test fine cold, but once hot they start to act up. Problem is, once you shut it down they cool off and by the time you are ready to test them they are back to functioning. If you have an infrared thermometer (the one you point at something and it can read/display the temperature back to you) then try pointing that at each cylinder cover after the engine begins to act up to see if you can detect which one is significantly hotter. That’ll be the one still firing.
Also, when running, and with it starting to act up, simply loosen the fuel cap. They are typically vented and if for some reason yours became clogged that can cause similar symptoms.
