I know exactly what you mean. I have bought so many parts and junk, that I could have bought a hundred motors already, I just dont have them.
I ask myself over and over why I do it. I make a point of putting aside a few bucks every month to buy a new motor or kit. At the moment I have several times the price of the new weed eater. But I have never bought one. Since I don't have a schedule or a customer to satisfy, this is like a mystery story to me. It's a challenge to see if they are going to beat me, or I am going to beat them. That's about the only thing I can figure. It's like my dad used to say sometimes you eat the bear and sometimes the bear eats you.
Let me give you an example. I got this one running in about an hour. Once I switched the carbs which I knew I would probably have to do from the start. Then I began to experiment with other carbs. I worked to long and my mind drifted off to making stupid mistakes.
I spent a whole day in my shop happily puttering around working on my mystery. Now, If I had not been doing that, I would have been watching daytime tv with my wife. Or wandering around like a homeless person with no purpose. It's why I keep working on the junk, to be honest. To keep me busy and my mind active.
I know that you are absolutely right. There is no doubt in my mind about it. I just need to stay in the game. I have said before I would rather build the bikes than actually ride them. If I can work it out, so that I spend less than a hundred a month on parts, then my wife never complains and I get to stay out of the house. It's the only explanation I have. Oh yeah I have destroyed new engines as well as old junk ones. They are going to be junk when I finish with them anyway lol.
Speaking of wandering around like a homeless man, there was this guy who used to walk up and down our street talking to God. Everyone was terrified of him, he went to the mental health clinic here and they gave him an old dead cell phone. They told him it was a direct line to God. Whenever he wanted to talk to God, just open the phone and speak into it. Strangers are no longer afraid of him. Building bikes is my cell phone I guess.