I hear ya in the fun build tip. Ive had newer bikes, and because they ran good, weren't basket cases, I never touched them, just rode them.
Now that Ive built a basket case with a shattered piston, spent 1g on the rebuild, and hard tailed it myself, unfortunately it doesn't look worth a shit, but you know, I'm OK with that. Its my bike I biult it the way I wanted, huge learning experience, first motor rebuild that miraculously keeps running, and it has more character than the whole peanuts gang. Doesn't feel robotic like the others.
Buy the motor. maybe not 400$, but of course look in the valves, yank the clutch cover. shrink wrap may or may not have been the best bet. could have held in moisture, instead of keeping it out.
Build another
you can always get your money back, rite?