carb bowl fuel drain line

This machine starts and runs 1/4 throttle,idles great, but under load wont pull past 10 mph tops.BOGS DOWN TIL U LET OFF THROTTLE THEN IDLES FINE..no backfire or such just wont go... i changed and even added a second fuel filter. blew airbox out and ran great for 30 mins and back to same ol...

I have a 2003 Sportsman 600. I have the four wheeler at another location and cant measure myself. I want to replace the fuel drain line coming from the bottom of the float bowl. The service manual mentions it, but does not mention the size of the line. Would someone happen to know what size...