I have seen at least one very nice XS650 with 125,000 miles on it, and another that I know is still on the road with over 100,000 miles on it. Mine looks great from a few feet away with 61,000 miles. It's all in the care it received somewhere along the line. Refreshing a top end isn't really that big a deal, now that I've done it.
My first had ca 70000 -80000 km 44000 Miles the top end .. one Cam shaft bearing was gone . The valves needed lapping at least
Cylinder barely got a pass from, the shop ..
The bottom end had a Crank Bearing Pitted A outer one Luckily
And the small end con rod getting a pass.from the Yamaha top mechanic.
The cam had damage on the edge of one lobe , perhaps usable but I replaced it.
Had I not stopped using it it I would get a major breakdown
I bought it 15000 km
So the 125000 miles I would believe be after 3 Rebuilds ( Jokingly ) Or after e very careful usage and perfect maintenance
Something that was very rare or non existent then
And Is not yours also rebuilt and having a replacement Alternator
Furthermore you are an experienced professional Mechanic having the tools and know how and place to do the top end Job.
It is not something everyone can do .. Engine out which is heavy work Disconnecting electrics and putting it back together with need for
Torque wrench that not everyone have Gaskets and parts shop work $ 2 - 400
Leaving it at a shop ?? 5 hours a $ 150 n hour the same Amount as the bike
This is the reason back in the day 18 years bought "Cheap " Bikes setting out with high expectations took them apart
and never got them assembled again..
Some had the tools and knowledge but the time place and the money was not there . Most of then having " Taken a hit "
scrapped the rip off oil leaking no compression fraudulent first bike . Bought a new or newer MC
5 year old tops. And still not so good on the oil change part ( Most of them )
So yes there can be 121000 miles bikes I have never heard of a twin but Can exist
On the other end No service and No warm up Hooligan ridden with poor Maintenance it is probably possible to run it down on 30 000 km
18000 miles.
Who can tell the odometer even can be tampered with
Check out what gggGary found that leading zero ... there can be good crank and gearbox in there .. Can be
Quick inspection swooping that in .And you can have + 10 -- 15 years riding
That I don't think is there on a 50 k miles bike