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Old 08-13-2010, 10:06 PM
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2door 2door is offline
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Default Re: How fast will a beach cruiser with 49cc 4 stroke motor go with a 155ib user on it

He might be right but I was thinking more like mach 1.2...or there abouts

In all serniousness you question is impossible to answer with any degree of accuracy. There are so many variables involved that we can only make educated gusses. The engines, although outwardly appearing identical, often display quite different performance levels. Anyone with more than a couple of engines will tell you that they all run different. I have one that will run circles around my others and the only difference I've found is ignition timing. The magneto rotors (magnets) are sometimes indexed differently on the crankshaft therefore advancing or retarding the spark. Other variables are rear sprocket size, tire diameter and inflation pressure, drive train alignment, Fuel/oil mix, altitude, rider weight and, it might sound funny but his/her width. More frontal area means slower speeds.
All in all 25 to 30 is a safe guess. Some have reported higher and lower top speeds but the 25/30 range is a good ball park figure.
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