Not to worry. I would suspect that your impulse line is cracked, or you have a scored engine. The impulse line is a PITA to get to on those saws. They drive the fuel pump on the carb. If they are loose or cracked, the saw will run like crap no matter what you do. Pull the muffler and look for scoring in the cylinder and on the piston. Light etching is fine, deep scoring will be pretty obvious.
I have had lots of 1123 saws (025/250, 023/230, 021/210). Like the 026, the 025 came with dual adjustable jets (H&L) as well as fixed H jets. The dual adjustable ones are better. All of them have the adjustable L/A which is the idle adjuster below the one or two jet adjusting screws.
What you want to do is reset the H & L carb screws to the default factory nominal setting. On the 025 that means turn the screws in and seat them *gentley* until the screw stops, and then back them off. Back the H &L screw both out one full turn. Start the saw (if it will start) and run it to warm it up with eth bar and chain on it. Then if you have a tach, set the idle to 3300 RPM. Then turn the L screw in or out to get the highest idle. Reset the L/A to 3300 RPM again, and redo the process until you get the highest idle from the L screw. Then turn the idle down until the chain stops (with the brake off).
Then set the H screw. At WOT, the saw should be set to run at about 14,000 RPM. It should burple or 4-stroke some at WOT. If it sounds clean, it is running lean. Do some cutting, and the WOT saw sound should clean up. If the saw bogs, adjust the H screw in or out a tad (1/16th turn) and do another cut to see if it cuts better. Do that until you get a good cutting saw with a burple sound running unloaded WOT. To see if the saw is running rich enough, do a good long cut at WOT. Then shut off the saw from WOT. Let it cool down and pull the plug. It should be chocolate brown.
If you do not have an adjustable H screw, all you can do is adjust the L screw. Run a tach to check the WOT speed, and it should be about 14,000. You can look for a dual adjustable carb on Ebay (I only have a fixed jet one left in my 1123 parts collection).
