Looking at older bikes 50's 60's early 70's what would you consider a well built frame? The first bike I built was a Columbia 1960's beach cruiser with a 66cc motor.give or take a few on the year. after about 60 miles on it I noticed the frame starting to crack. the crack is on the tube were the kick stand is and the tubes that go to rear wheel. sorry I don't know all of the terminology. it also looks like instead of welding the tubes they may have been brazed. is this common? So I would like to find a older bike that the welds are strong.