Am thinking this is the D003xxxxx serial number....as for being a lpg engine one thing to check would be the idle mixture adjustment...on the side of the "carb" where the lpg hose comes in from the vaporizor,there should be a large screw....turn this in all the way till it bottoms out then back it out 2 full turns to start..with engine running adjust as neccisary to get a good smooth idle...