We are doing this sort of trip at the moment 2 up.
Left the UK at the end of April rode straight to Stockholm and caught the Ferry to St Petersburg arriving right at the end of April. Weather was okay but decided against Norway as it was too cold.
Since then we have been to Moscow, Suzdal, Kazan, Samara, crossed to KZ, Uralsk, Aktobe, Almaty (via Astana), crossed to UZ, Tashkent, Samarquand, crossed to TJ, Dushanbe. So that has taken about 5 weeks, with plenty of rest days.
From there we are doing the Pamir, back into KZ, Barnaul for new tires and a service. Mongolia, probably Lake Bykal and then a beeline for Vladivostok to catch the Ferry to South Korea.
We are 2 up on a KTM950.
I should add that in hindsight I wish I had gone down to Aqtau and of entered UZ from the west, UZ was so much different than what I expected. Everyone was really nice, went out of their way to make us feel welcome and helped us when we needed it. Even the UZ cops, who dont have the best reputation were fantastic, when they eventually did stop us at a check point (waved us through most of the time) they checked what they needed and then asked a pile of questions about our trip.
I would loved to have spent time just cruising around and stoping at the small towns, drinking tea and eating fresh food, especially in the Southern part of the country. My wife went into the markets in Denov (Denau) and had a blast. So I would definitely consider adding this to any trip across there, maybe your return leg.