started and ran well for 5 minutes after cleaning carb and checking a plug that was decent.
Is the fuel in the tank old?
Is there rust in the tank?
You might have to pull the petcock to check the fuel screens. One may have dislodged.
If crap in tank or dirty fuel you may need to drain tank, carb bowl to get the crud out.
Wish I was there. Meh.
And lastly.
You may need a timing light. Not to time but to check that it's firing regular when it's acting up.
You should see rythmic strobes from the light that you can see increase/decrease with revs.
I have seen a CDI modules and ignition coils go thermal intermittent.
Still. I'm guessing from miles away
