I had a very troublesome XL2 in recently, owner wanted it running again... 120 PSI compression, good spark, I ended up replacing the crankshaft seals as the PTO side was leaking. Rebuilt the carburetor (Walbro HDC) and while the saw would always start and run it would not idle correctly.
Additional pressure testing revealed the oiler plunger/gaskets were leaking so I order a set from LRB, but is would still leak in that area and the idle issues continued.
I even tried a solid rubber gasket in place of the plunger, rerouted the oiler lines like the early models and no change with the idle issues.
I went over the carburetor several times, all ports were open, check valve operational, choke and throttle shafts did not have excessive wear, metering lever is set correctly, certainly no obvious problems there. Of course I installed new OEM Walbro gaskets and diaphragms.
Ultimately I replace the carburetor with another used, rebuilt (fixed H jet) version and the saw behaved as it should other than being pig rich on the high side.
I would really like to know what the issue was with the original carburetor.
Mark