Another fun one.... For a full how to rebuild a 505 check out this video I made https://www.youtube.com/watch?v=EfM7fkIju2k&t=92s This bike was a challenge, upon rebuilding it the first 3 times the output shaft seemed to be locked up, which it turns out was from the OG stock crank, a small piece of one of the lobes had chipped off and wedged itself under the shaft, under pressure this caused the shaft to bind, it took a lot of searching to find this issue, but its all buttoned up now. So I wanted to stay "stock" but the DS cylinder on this bike was rated for 20pmh, and that wasn't gonna cut it, so I rebuilt the motor and added a 50cc Athena, which is very similar to the stock D top end, but the intake that is included is funny, a stock square Bing doenst fit, a Puch style round Bing doenst fit, no Sha with any shim fits either...So I used a spigot mount VM18, which was WAAAY to much carb, swapped it out for a 14/14 Sha using a spigot. I also bounced between multiple pipes, a Peugeot circuit and a Peugeot, well some other kind of pipe, ultimately the larger pipe seemed to pair better with the cylinder. I also switched from points to a Tomos CDI w/Parma box, I dunno if the curve helps, but its whatever because I dont have to fuck with points, so win/win. So thats the motor, how does it run? Slow...Im fat and moped clutches have came a long way, off the line Sachs just cant cut it compared to all these supped up bikes with clutch mods, but it eventually gets up to low 40's and does so with reasonable head temps, maybe there will be a clutch solution someday...until then this thing is a turtle but always gets the job done, Sachs out!