Where can i buy a piston @barrel for a baumr sx66 chain saw

Baumr-AG Pole Saws Instruction Manual (datastreamserver.com)
Page 36 of manual says chain not to be spinning before trying to cut. Need pull trigger to start rotation.

Try to find a more local dealer, or use a place like Edisons Australia,
https://www.edisons.com.au/parts/
as they do ship worldwide, as long as you can pay for the shipping.

if you can't find one , be aware that the piston and ring will be generic fit for that cc engine so go to a mower shop with the bits and see if you can get alternate parts
for example I have homelite piston and ring in a husqvarna trimmer for the last 5 years and still starts and runs ok
as long as the bore size is the same and the wrist pin fits in the piston

up from the bottom of the cylinder
make sure that the ends of the ring is at the locating pin in the ring groove
pull the conrod right up and put a set of vice grips on to hold it up position the barrel over the piston and hold the ring in with your fingers
gentle push the barrel over the piston and the taper at the cylinder base will hold the ring in as you continue to push the barrel down
if you have failed to correctly align the barrel on assembly then make sure that the piston is at the top of the stroke before turning the barrel around as the ring ends may catch in the ports of the bore and break the ring.

Need a new pull starter mechanism/kit for Baumr - AG PNHT 4500 Professional Pole Pruner Saw

Is this machine mechanically sound, remove the muffler and take a look at the piston through the open exhaust port, any signs of scuffinf or damage to the piston skirt and the saw will have to come apart for further investigation.

I have just bought one and the manual is hopeless but finally I figured it out. If you have installed the chain and guide you will need to remove them, then with the saw lying on the side and chain cover off you will see two holes on opposite side of the oil tank/engine casing
This photo shows the spike in position.

where do u live

If you perform the labor repair likely <$20 (<$9 for pump, <$1 worm gear). Compare replacement cost to 34cc± replacement, your call.
A link to a Poulan 2150 Gas Saw Type 7 follows (may not be your saw):
http://www.ordertree.com/modelinfo/PWE/2150-Gas-Saw-Type-7/75.2150-Gas-Saw-Type-7.1.59.1.html

If the link is not your saw it can be found here.
The IPL (exploded parts list) for your saw is the only detail for the oil system and it is sketchy at best. Oil components and part numbers are listed but may be on different illustrations. They are also beneficial with disassembly/reassembly:
Poulan.com
http://www.ordertree.com/modelinfo/POULAN-WEED-EATER/75.59.html
The dash number of your serial number is the type.
The oil pump is under the outboard clutch, this is helpful with removal.
R² Drive Link Outboard Clutch by Drivelink.blogspot.com
http://www.youtube.com/watch?v=cdqkIuVNUQc

1. Check the IPL for your saw to see if any special tools are needed. Poulan (Craftsman, Jonsered, Husky) clutch removal tool part number 530031112 if needed, is under $5 from many sources (look at the visible area between the weights if 2 small round sockets are visible you need the tool).
2. There are metal piston stops available, when square (almost never) with the piston top these work well, if not square they have been known to punch through the piston. I suggest a length of nylon rope (nothing left behind) be used instead of the piston stop (retain 6" ± so you can remove it). Make sure the piston is near the top of the cylinder before feeding the cord or it can fall through the exhaust port and damage the piston as it rises.
3. Everyone I have ever removed had a left handed thread (tighten it to loosen it).

If you have more questions or need additional help please reply below and I will get back to you. Thank you for using FixYa and Good Luck. HTH
Lou

Loosen the chain tension adjustment screw a few turns so that the tang from the adjuster will drop into the large hole at the rear of the bar. You may need to jiggle the bar in and out a little to engage the tang. Once you do, the cover should drop into place securely. With the attachment nut(s) slightly loose, adjust the chain so that it doesn't droop from the lower side of the bar, yet still turns fairly freely by hand. Tighten the fasteners on the side plate and recheck the chain tension. Hope this helps!