Husqvarna 55 rancher-just put new piston ring and cylinder.saw start right up and idles.when i try to acellerate it bogs and try to stall.when I let off gas it idles fine again.I tried turning mixture screws but they both have plastic stops on screws [hi-red and lo-white-they didnt seem to do anything .changed gas filter,gas line,air filter,used hi test gas with husqvarna xp 2 cycle oil with mixture to specs,even tried new gasket for carb.only thing i was not sure of was i think i put the carb gasket on right but was wondering what the hole and notch in plastic mount housing for the carb was for does gasket cover that as i was not the one who took the saw apart got the saw already apart

Check flywheel key again, I've seen ones that were partially sheared, would not start. New key and they start right up

That sounds like normal compression. By removing the spark plug you are eliminating the compression in the cylinder therefore it will turn freely. Doesn't sound like a problem.

However, check that it is the right spark plug for the saw. If it is too long then it may enter the cylinder too far and be acting like a piston stop.

you may have a piston/ring problem causing no compression

You need to check that this machine is mechanically sound, remove the muffler and check the condition of the piston skirt through the open exhaust port, any signs of scuffing ( seizure ), and the cylinder will need to be removed to assess the damage

Before you do anything else i think you need to check the engine is mechanically sound, remove the muffler, take a look at the piston skirt through the open port, any signs of scuffing on the piston and it will require removing the cylinder to assess the damage, they are x torq engines, due to the way the air ports work they are quite prone to carboning in the piston rings, make sure it has plenty of compression.

I had a very similar problem with a stihl 029 farm boss.I did everything you did except I took it to a shop to do the piston and ring replacement. When I got it back the first time it would run for about two mins. then die.I fought it for a couple of weeks then took it back and expressed my displeasure. Then checked it all over and replaced piston and ring again and it runs great. They told me they could not get the right compression with the first one and thought the groove for the ring was cut to deep.I hope this is of some help to you. Thank you.

Likely, the saw has been run with straight gas--no admixed oil. When this occurs, the piston, ring(s), and cylinder wall will have been deeply scored. Remove the muffler and turn the motor slowly while watching the surfaces of the piston, ring(s), and cylinder wall. If these surfaces are not smooth, then replacement of these parts is necessary. (very expensive with parts and labor) Hope this helps!

The piston rings rely on the oil in the gas to lubricate the cylinder wall. More than likely, the rings are now too small to provide the proper seal for enough compression. It could also have worn the cylinder wall more than the rings, the end result is the same.

You can try to remove the plug, put in about a 1/2 teaspoon of oil into the plug opening, slowly pulll the rope 1 time to let the oil coat the ring & wall & then put the plug back in & try to start it. Use a little extra oil in your gas to provide thicker lubrication. good luck

Check the air filter and the muffler if either are plugged up it will not run smooth. Carb hi and low screws are very sensitive so if you change them, only move them a little at a time.

Clean air filter and try starting fluid through air intake if you have spark this will definetely start it......On the rancher , is the air cleaner clean??? Remember that all you need to make an engine run is fuel , air , and an ignition source .. When you attempted to start the Husqavrna by adding fuel to spark plug chamber this actually causes a no start or very hard start condition it will act like if flooded....What does help if you remove the spark plug pull the pullstart and ensure that no liquid (gas is coming out of chamber) if it is keep pulling until it does not.... then take your spark plug ,after you have cleaned and gapped it, and with a butane lighter heat the tip for approximately 30 seconds and then reinstall plug and give it a yank after you spray starting fluid in the air intake....Good Luck