there's a tire valve in the hose somewhere holding in the pressure, is it at the end that has the spark plug threads? if it's not and is up near the gauge, then yes, the hose length is making an impact on your compression reading, two stroke engines have a very short period when they are actually compressing the air/fuel mixture (distance between top of exhaust port and the end of piston travel)

how many times are you pulling the cord to get your reading?