i have an old mcculloch 610 it had a 16" bar, someone put on a 20" bar, it rips through just about anything without slowing down there doenst seem to be any problems at all but when i brought it in to get serviced i was told that I should buy a new 16" bar and put that on. When i asked why he could not provide a reason. Is the 20" bar a problem?
