Im just curious ?

I'm working on a for sale bike now myself, I will have customer sign a disclaimer which will state that they understand there is no warranty and also stating that the seller of the bike or no one associated with any of the parts on the bike can be held liable for an injury, death, or loss in anyway including loss or damage to any private or public property.

I will however give the customer an easy to read and understand instruction sheet for fuel mix and general maintenance.

Ill be willing to help with any issues for the first 30 days and in that time if there is a faulty part Ill be happy to replace it if it hasn't failed due to abuse of the bike or engine.

The engine put on the for sale bike will have zero high performance mods other than maybe a better head since keeping the engine cool as possible is a good thing for reliability, the engine will get a better top bearing, gaskets sealed well and the ports on the cylinder will be simply cleaned of burs, better engine mount hardware and the carb will be jetted down a little for a smoother running engine.

If the right things are done and kit that has been proven to have fairly good reliability is used, I think the buyer can expect to get good service from the engine if it is run right and the oil mix is always correct with a good quality oil.

I plan to set the for sale bike up for a 32:1 mix using a quality oil the is easy to find in my area.

Im thinking it all depends on the seller's conscience... or lack there of to build a quality product. One can build a decent quality bike if they source their engines from a reputable source then use higher quality parts in place of the parts with known issues such as that plastic spark plug boot for example.
then if said builder takes care of the initial run in of the engines and sells the bike once they're sure everythings in good order, head retorqued and set, mounts checked and re torqued if needed, chain re adjusted after the initial stretching etc... then the end User will have a nice reliable ride that'll most likely last for them.
Now if the builder just buys the cheapest kits they can find, throws everything together and sells it before even starting the engine just to crank out bikes, the risk of something going wrong is increased exponentially. These are the type that only care about the money, most likely would try too blame the customer to get out of doing a quick adjustment or replace a bad part etc.... I don't know how they can stay selling, but unfortunately they get enough customers who either don't know about their rep or just want one so bad they ignore the warnings etc.... but it also makes it more difficult for the honest guy to build and sell because people begin to think its the bikes or engines that are at fault and not those few who are in it strictly for the money.

What Map said... exactly... these are the kind of people who will do good selling bikes.