Comments by "David Elliott" (@davidelliott5843) on "Are 4-Stroke Bike Kits better than 2-Stroke Kits? Let's find out!" video.

@wvadam The two-strokes sold for bike frames are little better than stuff made in the 1950s. However a modern clean 2 stroke is not cheap but it would be cheaper than an equivalent power 4 stroke that's equally clean. Check out the Rotax ETEC used in Skidoos and Evinrudes. Very clean, excellent lugging power, good fuel consumption and makes 160bhp from 850cc. It beats the competing (very heavy) 1200cc 4 strokes on all levels including power and fuel consumption and easily meets the stringent USA EPA requirements. 2 strokes lubed by oil mixed in the fuel always suffer compromise. Full throttle = not enough oil without smoke. Closed throttle = no oil at all. They also stutter and missfire on part throttle causing pollution and the piston etc gets hammered about. Today's DI engines solve both problems and they don't produce a gallon of toxic sump oil every few thousand miles that (some) people pour into a hole in the ground.
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are they both the same cc?
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@deusexaethera Yamaha invented the varaible exhaust geometry "Power Valve" for their 250 and 350 twins Liquid Cooled "Elsie" twins. It's not really a valve as all it does is change when the exhaust port opens. Full up for high revs power and down for low revs torque. The inlets had reed valves which are atmospheric non return valves allowing more aggressive transfer port timing.
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@deusexaethera NSU used these on the 50cc Quickly moped engines. It's a decompressor to make starting it easier.
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