Piston, cylinder, head, intake, carb, rear sprocket, exhaust.......
Puch or Tomos, Most should apply but I did the Puch.
When you disassemble, keep track of your parts! Clean and lubricate your head studs and nuts or you may strip out the cylinder when trying to tork the head down. Replace the exhaust (6mm hex head - Puch) with studs, lock washers and nuts. (6mm, 10 or 1.0 pitch - Puch) and/or take one of the screws with you to the hardware store to find a match. While you are there you might as well get a new set of studs for your intake as well.
The stock studs were a little short so I got longer ones. The intake was a little thicker at the base than the stock manifold.
For the Puch two-speed ensure that you specify that you need the Tomos intake manifold! The 14mm intake you get with the Puch kit is only good on the 1-speed. Your carb will mount a little funny but it works great! And the Tomos is bigger. Basically you end up flipping around the intake to make the carb point at about 10 o'clock if you are sitting on the bike. A little ram-air action possibly :)
The Amal carb. It comes with a plastic spacer to reduce it's 25mm opening on the intake manifold side to fit your intake.
The main body thru the carb is 15mm. You can spend alot of time trying to reem it out or do what I did. I ended up cutting up different spray paint can lids until I found one with the right thickness to mate the intake to the carb opening. That worked for me but I suppose that any hard plastic would work.
Do the rear sprocket (if you are doing it) before you put the exhaust on. Common sense will tell you that it will be in the way. Make a note of where your wheel is currently mounted. You want it in the same spot when you put it back on and are shortening your chain.
While you have the rear wheel of you might as well re-lube the bearings. Be careful not to lose any. Check you brakes as well. This is the time to replace the shoes and/or the tire if needed.
Be careful not to overtighten things during re-assembly. I tightened until no more "jiggle" or horizontal movement could be made and then just hair (or RCH) more. Just check for free-spin before re-assembly. Sweating yet? You better have a clean towel. Go ahead and wipe your brow and then post a pic here.
Kiss/Motley Crue re-visited, yes? :)
Take off only ONE link at a time when shortening your main drive chain! Going from 40 to 36 teeth does NOT mean you take off 4 links! I just doesn't work that way. Same for the pedal chain.
If you do it right you won't have to touch your pedal chain especially if you have a tensioner. Most people will grind off one side on the chain to remove links. I just used a hammer and punch in a vise.
You want a little slack in your drive chain. Slowly adjust the wheel and then sit on the bike after each try. You will take up the slack with your weight.
Lube up the chain(s) again. Why? Look at your hands. Alot of the old stuff is there, huh?
Put on the exhaust. You may need to create a spacer for the rear mount. Do NOT try to bend the exhaust to tighten up. You may end up breaking the studs or cylinder. Make sure you put a lock washer here. Use your imagination. Washers will work but you can find better things to use at the hardware store. A tape measure (micrometer even better), pencil, and paper are great things to have here.
Tighten it all up, wash up, and fire it up. (With a new plug)
I hope this helps someone.