Well, it's not true that you have to take the engine out to adjust the valves, but maybe he meant "valve job", as in replacing valves. It also helps to drop the motor forward to take the carbs in and out.
Still you mention this word "drop" which I do not like.
So, since I drove today instead of riding, I'm taking advantage and just ran a load of hazardous warehouse chemicals to the local approved place for them. Honda dealer's next door, so I browsed. The new CT125 looks neato. Just like Uncle's old yellow CT90. Thought about it for a minute, till I saw what the dealer markup was. Ouch.