Bike suitability depends on your ability. There will be unmade roads, but if you stick to them there shouldn't be deep sand. Don't plan to go to Turkmenistan, visas are notoriously hard to get and half are refused for no apparent reason. Baku-Aktau is a better route but be aware the boat doesn't go to a timetable, it sails when it's full. You will need fuel range min. 400 kms as fuel is scarce and of low quality in Uzbekistan and the Pamirs.

The route you describe will be around 20,000 kms. That's very ambitious especially allowing for rest, servicing and sightseeing. You will run yourself ragged doing that. High mileage days are possible of course, but not advisable over a long period, plus on some of the poorer roads out there you will struggle to do a long distance. More than 300 kms per day (on average) is pushing it, and you would miss seeing anything in the places you're going. Who wants a trip where the only thing you see is the road ahead?

That said, this route should be a great trip if you allow enough time. I plan to do something quite similar, but going between the UK and Magadan, and not until 2022 as I think there will still be a lot of travel restrictions in place this year. You shouldn't need a carnet if you don't go through Iran, and the only visa you'll need to arrange in advance is Russia.

If you haven't already, have a good read of www.caravanistan.com which is a brilliant travel resource.

Planning similar route, albeit more slowly. For Uzbekistan lots of people recommend bringing a cheap fuel filter: Fuel Filter Funnel