Need to know best way to adjust carb to get maximum performance on my homelite XL12

Here are free UT10490 Parts Diagrams you can print:

https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/green-machine/homelite/chain-saws/xl12-chain-saw-ut-10490

Homelite XL12 parts manuals

There seems to be 1 to many numbers in the model # UT104654 is it possible that it reads UT10465A.
If so here is a link to the parts diagram for a Homelite XL12 UT10465A ,
http://www.jackssmallengines.com/help.cfm#/Homelite/XL12_Chain_Saw_UT-10456-A/Engine_Internals/1010129/0609011010046

Yes it is very important i would recommend also putting in a new spark plug. Thanks for asking and I hope it helps

Turn both screws CW to stops (lightly), then back out each CCW 1-1/2 turns. This should get the engine running if it will. If it does not, check the lower diaphragm on the carburetor for hardness or cracking. You appear to be running on prime only--the carburetor doesn't seem to be pumping in fresh fuel. You may need to do a carburetor clean and re-kit. Check the fuel line condition and the fuel filter in the tank for plugging. Make sure the muffler and air cleaner are not plugged. Once you get the engine to continue running, warm the engine up. Open the throttle and adjust the H needle CW--the engine should start to speed up, but still 4-stroking. The proper setting is 4-stroking, but immediately 2-stroke when cutting. Release the throttle and adjust L needle CW so that the engine runs fairly smoothly, yet will allow the engine to 'follow the throttle'. Set idle speed screw so that the chain stops turning, but the engine continues to run. Hope this helps!

32:1 (1 gallon of premium fuel to 4 ounces of quality 2-cycle oil) according to this
http://www.acresinternet.com/cscc.nsf/ed1d619968136da688256af40002b8f7/a17d735d551f0f1e88256b78005f6a7b?OpenDocument

It will operate better on 50:1 (1 gallon of premium fuel to 2.6 ounces of quality 2-cycle oil) once adjusted. HTH
Lou

The procedure is logic and common sense buoyed up with as much information as you can obtain.

This is a typical fuel system and a tip or two:
http://www.fixya.com/support/r3706813-2_cycle_fuel_system_repair

The IPL (exploded parts list) for your saw is the only detail for fuel line routing and it is sketchy at best; components are listed but may be on different illustrations. (About 30 XL-12s; I defer to you)
Homelite/Ryobi.com (authorized parts supplier)
https://www.gardnerinc.com/recons/disclaimer-lg.php - Agree; Choose “Product Line”; “Select OEM” & “Select Catalog” both to “Homelite Consumer Products”. A drop down list appears; self explanatory from here.
The numbers Homelite & Ryobi use do not match the numbers everyone posts. A careful inspection of your saw should find something that matches. Good Luck. HTH
Lou

most new homelites etc have the high speed screw too lean because of epa standards---you usually need a special tool either a splined or pac man screwdriver to open the adjustment screw another 1/4 to 1/2 turn to get the right rpm's

You need to disassemble the carb. and spray with carb. cleaner. If you need tips on how to do this, just let me know. You may need a new carb. kit as well, but we won't know that until you first perform the first step, or if the carb. parts are more than 3 years old. If they are, then go ahead and buy the carb. kit and replace the parts.

Jim

The preset is to turn them all the way in (Don't tighten them hard or you will damage the needle) and then back each out 1 1/2 turns. This will get you started. You can then run it at full throttle and turn the high speed jet in untill you hear a change in the RPM. Then turn it out untill you hear the same. Find the happy medium.