They were built in 1976 & 1977. They have crappy brakes. I really don't know about the engine. Mine runs great. I've never had any problems with it other than brakes. I have a neighbor that has one as well and tells me pretty much the same thing about his. I've got the manual for it so if you'll give me time to dig it out I'll see what I can find out about the engine. I think that they were a interim between the "54" series & the better "74" series.