Hey you blokes, Nadine and I did this last year on two Chinese 110 cc C90 copies. It took us two months to get to UB and that was riding every day that we could. We could probably have done it a bit quicker had it not been for unpredictable things - heavy and unseasonal snow in Bosnia in May (30 degrees c one day, - 2 and 20 cms of snow the next), Russian police who just wanted to look at our bikes and marvel that such crap machines had come so far, locals who wanted their picture taken with us at fuel stops or pee stops (I jest not), the sheer enormity of Russia, hours at border crossings, and the appalling or disappearing roads that slow you down; the is no way round them. Time spent all adds up and eats in to the time you plan on getting there. Your bikes will make it - ours did - but the problem you might have is that whilst little bikes can be better than big bikes in many ways in terms of being light and nimble and easy to fix, you won't have the luxury of being able to cane it and make up the miles when you do get a good bit of road. And no, you won't be able to risk riding at night - you'll understand why when you get there. Make sure you take spare spokes and if you don't already know how to, learn how to replace broken ones.