air-cooled RD350 spark strength

[2t Fan]

Using vintage smoke ignition with Dyna coils and a 7A new battery. off late the spark strength is not great. too much white smoke from exhaust. Using 25ml of Motul 2T / ltr of petrol. 27.5 pilot, 205 mains, BR8HIX plugs, banshee reeds.  I can also see a voltage drop on the digital volt meter. 12.3 volt at idle and around 13.5 (+/-) during running. sounds good ? if not what to check

[m in sc]

that all sounds fine. see if it gets better with regular plugs. what is your gap set to? i mean if its smoking its being ignited.

[2t Fan]

Plug gaps around 0.6mm . Sometimes I can see the battery voltage dropping below 12 volt. Do I need to replace the alternator brushes?