Links I’ve found that contain very important QT50 information
Replacing crank seals without removing the engine on a QT50 – scroll to bottom of page
Installing a 60cc or greater kit on a QT50 and making it work – tips
From the mouth of xrongor, QT50 bonanza of golden information. Scroll up to top of page and read his posts.
I made a pdf of it just in case it ever disappears from that site.