Garage pixies will often fix faults when you take a toilet break. They use all the tools they have stolen. I was chasing a fault on my T120r for several weeks where the bike just would not pull above 4000 rpm. I replaced many items and the fault stayed the same until i left the bike alone a few days and then it was fixed.
next fault, i will lay out all the spares i have and leave the garage for 3 days.
What would seem to have been a problem was the old NGK plug caps. I replaced them with new and the bike resumed normal service. However, the carbs are very clean now and tappets adjusted well, timing checked and new Boyer unit fitted and new coils. A battery and a voltage regulator. I had most of this in stock so cost very little.