RUS visas cannot be extended.
New ones can only be applied for from outside RUS.

Exiting with an expired visa will almost certainty incur fines (or bribes) - after considerable delay. I know of one person who exited a few days over - he was held for about a day and relieved of a fair amount of money (I can't recall exactly but think it was several thousand roubles - I'll check and update this post).
The greater possible longer term consequence could be the refusal of future visa applications.
We are talking here about exceeding the actual visa validity period - not the 90/180 day condition on Multi entry ones, which has been of no consequence to myself or others I know.

The bike's Temporary Import Certificate can be easily be renewed at local Customs offices on production of paperwork only (not the bike).

I am not sure exactly where you are but there are strong motorcycling communities in Khabarovsk and Komsomolovsk as well as Vlad. They are all every helpful and extremely resourceful and helped us with repairs - even getting a replacement rear shock absorber mounting lug machined in a local aircraft factory using only the mashed up remains and photos in the manual for guidance!

Tom will do all he can from where he is (PM coming). Japan or Korea have BMW dealerships and are nearer to you, but customs delays probable. I know of someone going from Soeul to Vlad sometime next week -I will tell him of this thread.

Good luck.

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