Picked up on very nice, clean model 17 yesterday. The owner started it but took several pulls to get it going. She idled nicely but did notice it was revving quite high when he gunned it. He did say ever since he got it back from a guy who works on saws few years back it's always difficult to start. Brought it home, looked over some more and immediately noticed the carb is different, has a HL-1A instead of HP-1A. The sensing line for the carb is pitched off near the back of cylinder and the governor is disconnected. Question I have is what's the difference between the two carbs besides no sensing line. I'm a little hesitant on running this thing since there's no way to control the rpms. Thanks!