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Hello. My name is Tan.
To find the issue you will need a timing light. Connect the timing light to the top cylinder. Run the engine till it start to act up. Watch the flash of the timing light. It should be a steady flash with no dead spots. If you have a misfire it will be noticeable in the light. If you seee a misfire move that coil to the other cylinder now do test again. If misfire moved then that copil is bad. If the misfire stays then you have another ignition component failing. This will require further testing with an ohm meter.
Now while you are testing the spark choke the engine when it is acting up. Does it run better?
If no change squeeze the primer bulb. Does it run better?
Do these tests and post back with findings.
They way your explaining the issue it is acting like an intermittent ignition coil.