kind of a driver thing where the two strokes were concerned. i still have all my shop manuals, worked on many, didn't want to keep any of them. toss everything you think you know about two strokes if you want to work on them though. hell, just toss everything you ever thought you knew if you are like me and first set wrench on one when you were 23. impressive by the power they put out and what they weighed though. the design on the 53 and 71's which were so common really was from the 30's and when you considered what anyone else was building then, and you were a trucker who wanted payload and power, they had a reason for being. most of you never touched the 110's the 149's or even knew you saw them as they didn't get on the road much. you would have realized what noise really was though. 92's, penske, and the epa were the death