OK Eric,Lesson in being a good mechanic.NUMBER 1 ,when tearing down an engine replace everything.
Think like this ,everything inside your motor has been wearing out ,for the same about of time,same heat cycles ,same wear and tear.
Even if it looks ok replace it, murphys law says what you dont replace will fail soon after your build is finnished.
And that rule will help you build an engine that is dependable and lasts.
Hope that helps George
Cam chain an tensioner are always a good idea to replace in a tear down unless you know the history of the part. For instance if you know for a fact that the cam chain is fairly new and inspection reveals that it has no werid wear on it then you can leave it. If you got the bike and have no idea about the history of the chain and tensioner I would go ahead and replace it. inspection is key.
Ussually ,parts that are known for breaking or wear fast,they make up grade parts for.I always compare, how long the part was working for you for, before it broke or wore itsself out.
Compare that, to what use ,strain you plan on putting the bike thru in the future. To determine if the upgraded parts is needed.
Every one playing with old bikes have to keep telling them selves these bikes are not new they are old and getting older.How ever they are super over engineered units that should still do its work.
If your racing you should fit racing parts ,race stuff is power band specific.
Compared to street which operate in a ,wide power band.
That is very important, as most ruff running ,cant get out of thier own way ,loud ,bad idling machines, are from poorly chosen race parts fitted to a street motor. However if you choose wisely, racing parts that are heavy duty, will be good in a street motor.
Stock motorcycle engines rebuilt to as close to factory specs as possible will give you a great running motor on the street .
Most people will never use the stock motors full potential on the street.