The phenomenon of rust! Wtf. I've now cleaned out two step-thru mopeds. A 77' Sachs and a 80' puch. Both yielded different results about a year apart.
Tank was rusty but not that bad. It was stored inside. I read the wiki and went with the vinegar over the course of a week and it worked really well. I kept the tank full of pre-mix and the rust stayed away. Even when the moped sat over the winter the rust stayed away, even with the tank half full the rust stayed away. Problem solved.
I bought the moped fully running and working. The tank was rusty but not full of rust. I went with the vinegar again and got a ton of rust and chunks of crap out. Then the thing flash rusted on me. Guess I dident get the premix in in time. Rode the moped fine for a couple of months and noticed it bogging down at times. Felt like rust was just building on the jets. Sure enough it was. Inspection of the tank after cleaning the carb and I noticed more rust.
I went with the muriatic acid this time and boy is that stuff nasty. Left it in overnight and then drained it out. Tank was spotless
Except for some chunks at the bottom
Of the tank. I worked fast and noticed some light rust begining to form. Got the premix in and I think I'm good. I'm going to let it sit for a few Hours and see what happens.
I live in NY, near the beach. Salt air is a bitch.
I guess I'm just wondering why one moped would be almost rust free well over a year since it was cleaned and the other moped would just not be as receptive to rust removal.
Thought this would be a good thread to share thoughts and ideas about the topic.