they came with 16-28" bars. so the largest i would do is a 28.. i stick pretty solid to what the maker claims to be the largest bar.. this is for several reasons.. you may have the POWER for a longer bar.. but is your OILER up to it? and also those crank bearings! there is alot of factors to this.. the longer the bar/chain the more stress on the entire engine and every single one of its parts. being 103cc, you might get away with a much longer bar.. im only pointing out what the spec sheet i found says. being an older saw.. i wouldnt stress it out TOO much. treated well old saws can last darn near forever.