Check that your fuel filter is not partially blocked.
Carby jets clean? [if you ran the tank dry you have probably picked up some of the crap that normally sits in the bottom of the tank]
Also when did you last clean/replace the spark plugs?
Start checking the "easy" stuff first.
Things like rectifiers and other less likely stuff comes after you have checked the basics.
Mechanics always try to "fix" the expensive stuff first, then keep you coming back with more money while they continue to drain your wallet in search of the problem.
Find an "old school" mechanic who runs a workshop that works on all brands and ages of bikes, they are the ones who know their stuff and won't rip you off.
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