That type of HL was used on the RA`s fairly commonly, the T shaped high speed adjuster was referred to as the, alternate main adjustment needle. That needle can be left in the closed position and the carb tuned with the two regular adjustment screws and if the saw started running too lean during a heavy prolonged cut the operator could open the T handle one a 1/8 to 1/4 turn to richen up the mix without having to use a screwdriver on the regular main jet. I learned this from our original IEL - Pioneer dealer`s mechanic during the early 60`s. He also claimed the saw would run and act normally if one was to completely close the regular slotted adjustment screw and just tune and run the saw on the T handled adjuster, I have done so on several of my older saws that has the 3 adjuster screws.
