Came to me due-to the "rear brake pads" post:
We're buying new motorcycle, after 3,4,7,10 Previous owners and we don't know what changes has been made:brakes, carbs, camshaft, electrical wire changes, coils, Etc.
What you can say about that?
What to do?
what your 2cent?

my guess is that you have to go with the flow...

I got my 907ie with 2 previous owners and my SS had 6... the 907 was pretty original, not perfect but it was OK.

The SS , on the other hand... was...umpf...

I could not send it back as received it few months after the purchase as a Xmas present from my father who is quite capable to buy cars and bikes (he has a nice collection of vintage pieces) but in this particular case he committed the "sin" of trusting the seller-friend (EX-friend now ) rather than checking with his own eyes and it was sort of bad (mostly cosmetics and some bad maintenance)

WHat I did? Just rode them like they were new and dealt with issues that came about... and tried to enjoy the rides instead of focussing too much on the past

What you are saying, everyone know, when you buy vehicle, you know the previous owner give you his illnesses.
What i'm saying is of the good stuff:
does the carb is still weber or not? does the electricity has modified with relay, connectors and wires? are the coils replaced with the SS? or the calipers?
some modification checklist should be made for what original and can/should be change.
further than that:
Engine rebuild....camshafts? I can't order in advance and save time, maybe i have a sporty cams?
on my motorcycle i can see the brake lines was changed to stainless steel, but this is easy.

no, what I meant to say is that, whatever past a vehicle has, the first thing is to check the maintenance and safety, then ride / Drive it.

then and only then you can worry (if you need to) about it.

I agree.

Safety for the rider and the bike first. Wheels won't fall off or blow out, brakes can stop it, is there oil in it.

Unless you're psychic there isn't any way to tell exactly what's inside unless you tear into it. Even if they have receipts you'll only confirm the parts are there once you see them.

As you say, brake line upgrades are easy to spot as are 17" wheels. Carb swap requires a bit more digging. My bike had been updated to the newer cam pulleys and belts. Anything else you either have to trust the paperwork or you're going to get a surprise.

Hope for the best, plan for the worst.

The quality of the motorcycle is almost always reflected in the price. It is rare that you will ever buy a bargain, if it is cheap - expect plenty of work to restore it to a reliable and useful condition. Bikes are fairly easy to assess and it is equally difficult to 'hide' faults if you just test-ride it and have a close inspection.

I think you get to a point where the ever growing list of previous owners becomes a bit irrelevant and your left to deal with what is physically in front of you, and you have to be prepared to shift your expectations around a bit . If it does not have the mod you are looking for ( main relay ) it doesn't have to be a deal breaker because its not hard or expensive to do and you will have the satisfaction of making your 1st positive mod, and the next thing you don't like can be the 2nd.......embrace it mate .... takes us back to a time when a reasonable working knowledge of one's steed was of great benefit , and there is the piece of mind knowing for sure things are as they should be

I bought the book. The Ducati Paso 750 service manual, in several languages, and compared what it said to what I have on my bike. When it didn't match up I asked questions here, or it was obvious, like the Mikuni 38 mm smooth bore carbs. Mine ended up having all the upgrades like the relay for the coils and starter, upgraded charging system. Had a new rebuilt engine!