I've had both bikes, and currently have an 800GSA and a Sertao

The "chinese engine" rumor mill was rife with the early Sertao's but I've subsequently been told that the engines are back in Germany again. There were issues with decompression lift and the "beak" in the early bikea, all were remediated under recall by BMW. Even if the engines were made n China (Kymco I believe) they'll have bee done to a BMW / Rotax standard, not "cheap as chips" approach.

I've ridden the Sertao all over the place, on and off road in the past 12 months I've had it. Its a good compromise for someone wanting to do a mix of tarmac and trail, and performed much better than I'd expected. The only mechanical change I made was to put a DID chain on to replace the usless stock BMW one, and that was for ease of repair more than anything. Tyres swapped for TKC's. I rode the Sertao from NW UK through Spain in the summer, on and off road, in temps above 40 deg celcius which made the fan work most of the time, with the bike laden, plus 18 stone of me on board No issues, 70 plus mpg, and very enjoyable. Two people I ride with have swapped their current bikes for these subsequently base don what they saw it do and perform.

As for the 800 - superb bike. For touring its amazing, and hence the 800GSA is a super upgrade on the standard 800 in my view. The engine (as in the 650's) is a Rotax design, and you'll see all parts (even from BMW) are Rotax branded for both engines. Much sweeter to ride as its a twin, but with some extra weight

Cheers

Iain