You may be a bit lean on the lsn. Do the fuel line pinch test. The engine should rev a bit and then die in 2-4 seconds. If your on the 2 second side, richen it a 1/16th turn. If your on the 4 second side, lean it a hair. Other useful info to help you out would be temps, how much smoke are you getting and how does the rig run other wise.