Before spending 12 weeks in Arkansas this summer I filled the cylinders with Marvel Mystery Oil and let them sit. A week ago I pulled the heads and related pieces off in an attempt to "free" the pistons in the bores. I found that a lot of the oil had seeped out so they were no longer full of oil. I worked the transmission into high (4th) gear and rocked the rear wheel in an attempt to move the pistons but to no avail. I then used a wood dowel and gave each piston head a little "wack" to hopefully shock the rings free but again to no avail.
I reassembled the engine top end and left out the push rods this time to assure no valve openings to loose more oil. I filled them to the brim with Mystery oil through the spark plugs and sealed her up for another soaking session.
This time I removed the carbs, air tubes, exhaust system and all related parts to speed up the tear down next time. I labeled everything and stored the pieces in a sealed container.
I've been monitering oil loss this time and things are holding well. I added maybe a couple of ounces to the left side cylinder today and the right jug is still full.
The Zundapp Pistons each have 5 piston rings on them so I have been told so there are more rings / rust holding onto the cylinder walls. Hopefully a few weeks of soaking will free things up.
The other day I removed the hacked up shifter linkage which was on the bike and installed a nice original ($80.00) linkage assembly. This "new" linkage has a bit of surface rust to be removed but it is in nice condition. I also found a reproduction headlight ring on EBay a while back. I haven't installed it but it appears identical to the beat up, dented original on the bike now.