So - 2019 London - Beijing
In general...

A group "expedition" - organised by a company called GlobeBusters. For the last decade or so, every 2nd year they do a London-Beijing trip, and every other year - Trans-Americas (Alaska-Patagonia).
I would recommend them - they did a great job of organising, support, etc. One thing to note - it was rather pricey, and that would mostly be down to using very high-quality hotels (where possible)... my ideal would have been a cheaper trip, with cheaper hotels, and maybe a nice 4-star once every week or two, whenever stopping for 2 nights - to get a good break/laundry-done.
Started off from London's Ace Cafe with 20 bikes (mostly BMW GS, 3 Triumphs, 1 Ducati, 1 Honda CB500) and 2 support vehicles - a pimped-out Hilux, and a Mercedes van big enough to take a bike (or two at a pinch). The group was larger than I'd expected/hoped... and it did slow things down at borders or when choices of petrol stations was... limited.
But - it gradually shrank over time...
2 bikes had opted to only go as far as Almaty, another 2 only as far as Lhasa, and 1 guy came off with about 10 days to go - breaking half-a-dozen ribs, mangling his front-forks into a shape they definitely shouldn't be, and choosing to fly back to the UK rather than "be a tourist" by riding in either support vehicle or catching a train to Beijing.
Ace Cafe at each end gave us a decent send-off/welcome.... London shouted us fish'n'chips the night before departure, and then breakfast the next day - with speeches and such bollocks
Beijing welcomed us with bottles of cheap bubbly to spray all over the place, sweet cold beers, a decent spread, all sorts of "merch"... and speeches and such bollocks

Western-ish Europe...
From London to Turkey is a vague memory, but...

UK, France, Germany, Slovenia, Croatia, Bosnia-and-Herzegovina, Albania, Montenegro, Greece
Most of it was just getting the miles under the belt, trying to get out of Western Europe ASAP... quite well planned though, to keep the interest up... typically being a couple-hundred miles of motorway, and then an hour or so of some sweet twisties or country-roads, or something else a little more interesting - before reaching the hotel. So each evening, the recent/residual memory was the "fun bit"

Turkey...

3 nights in Istanbul - the first time we'd stopped for more than a single night. I'd never been before, so ticked off the major touristy things
Safranbolu - nice enough old town, with an absolutely shite museum
Cappadocia, Mount Nemrut & Ani

Georgia-Azerbaijan...

Tbilisi - rather cool city, very unexpected. Very "bohemian", or "hip", or something... without (much) wankiness that typically comes with those words. Reminded me of a less self-aware Melbourne. Plenty of the old-world stuff (ancient statues, cobblestone streets, bathhouses), and then craft-beer pubs, weird-modern architecture, wine-bars.
Oh - and look up the 1907 Tiflis Bank Robbery
Azerbaijan - the sign from Georgia announcing that you're approaching the Azerbaijan border also proclaims at the bottom "Good Luck!". An excellent little dig at one's neighbour
Caspian Sea - we caught the "ferry" from Baku to Turkmenbashi - a 13 hour crossing

The 'Stans

Turkmenistan - interesting. Probably most people's choice as "least favourite country of the trip" - but it would be a contender for my Top-3... solely as it was interesting. This is a country where it's essentially still a totalitarian rule... by a nutter.
Roads - mostly pretty shit, extended periods where they seemed to have laid black glass instead of tarmac. Not cool in the rain - we had one GS go down at reasonably high speed, no major damage to rider or bike
Uzbekistan - stopped at several classic Silk Road towns - Khiva, Bukhara, Samarkand
Tajikistan - Probably my favourite country...
The Tunnel of DEATH! - which was an interesting experience, but not one I'd want on my daily commute
The adherence to Islam was very much waning this far east, and some of the ladies certainly had that "adultery-isn't-really-that-bad-of-a-sin" sparkle in their eyes
The (bike) riding once we hit the Wakhan Valley/Pamir Highway... awesome. Riding along the Afghanistan border, unmaintained dirt roads along hill-sides, following rivers... so much fun... videos to come
Kyrgyzstan - the first peek at high-altitude passes, and fermented horse-milk. Some reasonably fun rural dirt roads, absolutely crazy drivers, and corrupt traffic-police armed with speed-radar-guns.
Kazakhstan - pretty much just a few days in Almaty, resting

China...

Border Crossing, at high altitude - a full day to just get physically across the border. Then 2 days stuck in Kashgar, getting the bikes' paperwork sorted.
Xinjiang province - oppressive. Police checkpoints everywhere, a very very police-state feel about the whole place. I probably shouldn't write too much about it, sitting here in a Beijing hotel not using VPN, but... look it up. Xinjiang, and the "Uighur problem".
Tibet - the story goes that Tibet is now essentially "pacified" - and the guy that managed that, has been moved on to Xinjiang.
There were certainly far less police checkpoints, etc - but still some
But anyway - Tibet... awesome. Altitude, obviously. Snow-riding - not fun, when I'd swapped the visor out for goggles during the previous dirt road sections.
Mount Everest - I've already posted about that... just awesome. The mountain itself - just being there - literally brought tears to several bikers' eyes. And the road to get up to Base Camp... motorcycle heaven. So many switchbacks... and chinese road rules - so safe overtaking is very much optional.
And then - the Tibet-Sichuan highway - the G318 - some sections, contenders as being even better than the Everest Base Camp road. On a bike, dodging chinese fuckknuckles in Land-Cruiser-Prados - just great fun.
Sichuan - some decent scenery, but the roads were already becoming rather "tame" compared to the previous month or two... so just ticking off tourist boxes on the way up to Beijing... Chengdu - pandas, check.
Shaanxi - Xi'an - great city, with a couple of days off to rest/relax/drink, and more of the touristy stuff... Terracotta Warriors - I'd seen about 15 years ago - not a single bit of more excavation has been done since then, but there are shiny new restaurants/souvenir-shop complexes.
Shanxi - at this point, we're just trying to get to Beijing, on roads absolutely rammed full of the infamous "red trucks" - what are presumably state-owned trucks, shipping coal from mines to power stations. Hundreds of them... thousands. I've got a video where I passed about 200 of them all queued up. So - lots of trucks, lots of coal-dust... doesn't make for traditionally enjoyable riding. Does, however, make for some very inventive interpretation of road rules at times... I was swerving up onto pavement to get around trucks, nipping back from the wrong side of the road into the middle of a police checkpoint, taking shortcuts through building sites, rice-fields, whatever.
And finally Beijing - made it, 16,500 miles, I think I remember my GPS unit claimed.
Beers were had.

The Silver Fern

Kruse