The most frustrating part about owning an old bike is when the bike is seemingly "possessed" by evil mechanical spirits.
I mean, you take the bike apart with hours and hours of labor, and send the critical parts (motor, trans, magneto, etc) out to experts who have an excellent reputation, or maybe you're good and you do it yourself, and do it right, then you spend weeks or months putting everything back together and tuning it up and spend $2500 doing it and assume you're good for 5 years of hard riding.
..... and 3000 miles later, the pistons are slapping or the oil pressure goes away or the bottom end starts knocking and you have to start all over again and decide whether to drop another $2500 down this bottomless pit ...
Luckily it doesn't happen too often, but when it does, it's enough to make you want to pitch all the old bikes in the skip and buy a Kaw Versys or a KTM or something ...
Lannis